Oakland Athletics fans have at least one thing (and maybe only one thing) to be excited about right now: Mason Miller.
Miller, 25, has been the best reliever in baseball so far this season. But what makes him a fascinating player isn’t just that he’s sitting down opposing hitters with ease—it’s how he’s doing it.
Miller throws harder than any pitcher in baseball right now. Way harder. His fastball averages 100.7 mph, the highest velocity in the majors. He’s thrown 97 pitches of at least 100 mph this season, 40 more than the guy in second place (Michael Kopech). He’s thrown 19 pitches of at least 102 mph. All other pitchers in the big leagues have thrown eight such pitches combined and no one else has more than three.
As if that wasn’t intimidating enough for hitters, Miller also throws one of the best sliders in the game. He ranks 10th in the majors in average vertical drop and 22nd in average horizontal movement. That means hitters have to anticipate whether Miller is going to throw them the fastest pitch they’ve seen all year or a breaking ball that disappears off the face of the earth. No one has been able to figure him out yet this season. He ranks second in the majors in whiff rate and seventh in hard-hit rate.
Miller’s first outing of the season came in mop-up duty in the ninth inning of a 12–3 loss to the Cleveland Guardians. He allowed two runs on three hits. Since then, though, Miller hasn’t allowed a run—a stretch of 11 straight scoreless appearances. He’s also allowed just four hits total over that stretch, and he hasn’t allowed an extra-base hit in any of his last nine games.
Wednesday afternoon’s game in Oakland was more of the same, as Miller mowed down the Pittsburgh Pirates in order in the ninth inning to lock up a 4–0 win for the A’s. He threw just 10 pitches, eight of which were strikes. He totally baffled Henry Davis with this nasty slider and got him to strike out. The other two outs came on harmless ground balls. It wasn’t a save situation, but it was his 11th straight scoreless outing.
The A’s, expected before the season to be the saddest team in baseball, are actually off to a pretty good start. They’re 15–17, which certainly isn’t great, but the bar is different for a team that went 50–112 last season and is currently playing games in front of a 90%-empty stadium as it prepares to ditch its longtime home in favor of a minor league park.
Oakland’s bullpen is a major reason why it has found that unexpected level of success. Last season, the A’s ranked dead last in bullpen WAR at Fangraphs. This year, they’re third. Last year, they had the third-worst bullpen ERA in the majors. This year, it’s the second best. And it isn’t just Miller. Veteran Austin Adams has a 1.86 ERA in 14 appearances and Lucas Erceg has a 1.42 ERA in 13 games.
As dire as things are for the A’s right now, Miller’s emergence as an elite shutdown reliever gives them hope that, whenever they decide they want to try to start winning again, they’ll have an unstoppable force at the back of the bullpen.
Anyone who’s ever started a new job knows the feeling. You’re new to the area, perhaps you don’t know the workspace layout very well. Coworkers’ names prove elusive. Maybe you do something mildly embarrassing to leave a shaky early impression—for example, in the case of Baltimore Orioles outfielder Colton Cowser, throw away a treasured keepsake of your nine-time All-Star closer.
There’s a reason they call them rookie mistakes: It’s because rookies make them. A lot of them.
But fear not, newbies, because the 2024 season is now more than a month old, giving plenty of opportunities to shake off the early butterflies and settle into your new lives as big leaguers. To mark the occasion, we present to you the first edition of Sports Illustrated's Rookie Roundup. Each week, we’ll check in on the latest from the game’s standout first-year players, alternating between the American and National Leagues.
The idea is to shine a spotlight on the best (and most entertaining) happenings from rookies far and wide. We’ll cover the headliners, of course—and with the steady influx of young talent, there are plenty of already big names to track—but also aim to uncover hidden gems making names for themselves as the season progresses.
This week’s focus is simple: We’ll highlight the five best AL rookies so far, with the NL’s top five coming next week. All of the players considered have, of course, made their fair share of rookie blunders. But they’ve made up for them (and then some) with their stellar play to this point.
1. Colton Cowser, OF, Baltimore Orioles
Baltimore’s organizational rebuild (read: tank-a-thon) from the late-2010’s resulted in the franchise picking in the top-five of the draft in four consecutive years from ’19 to ’22. One of those picks turned into Cowser, whose 26-game debut last season (with a .115 batting average and zero home runs) left a lot to be desired. Named to the Opening Day roster by manager Brandon Hyde after posting a 1.136 OPS during spring training, Cowser seized an everyday role by the season’s second week and hasn’t looked back.
Cowser’s hitting profile is a modern twist on the "three true outcomes" template: lots of walks and strikeouts, sure, but plenty of hard contact (rather than merely home runs). His 34.3% strikeout rate is the eighth-highest among players with at least 90 plate appearances, and his 38.1% whiff rate is the seventh-highest. But a quick glance at his Baseball Savant page shows plenty of red bars, as Cowser’s barrel rate, hard-hit rate and expected slugging percentage all rank in the 90th percentile or better. Combine all that with a 10.1% walk rate and excellent defense, and Cowser could follow in Gunnar Henderson’s footsteps and make it back-to-back Rookie of the Year awards for the Orioles.
Miller has struck out 29 batters in 14 1/3 innings so far this season.
Reggie Hildred-USA TODAY Sports
2. Mason Miller, RP, Oakland Athletics
If they gave trophies to teams for putting together five-and-a-half weeks of mediocre play when almost everybody in the baseball world expected nothing short of total ineptitude, the Athletics would get one. The franchise is in an abysmal position, with an owner resolved to move the team to Las Vegas and coming off consecutive 100-plus loss seasons. While the roster is low on household names (an A’s staple as old as time itself), the team has outperformed projections to this point with a 17–18 mark, and Miller’s been a key reason.
A five-year college career spent at Division III Waynesburg (with one season at Gardner-Webb) didn’t keep Miller from being drafted by Oakland in the third round in 2021. He logged just 28 2/3 minor league innings from ’21 to ’23 before debuting in April of last year. Miller pitched in 10 games for the A’s last season—six of them starts—and impressed enough to make the roster out of spring training this season as a part of the bullpen.
That’s an extremely truncated acceleration timeline, which is sort of fitting given how quickly Miller has ascended into becoming the league’s most dominant closer. His fastball averages (yes, averages) 100.7 mph, and he’s struck out 29 of the 54 batters he’s faced this season. Miller is a perfect 8-for-8 in save chances, helping Oakland to a 7–5 record in one-run games. His FIP currently sits at -0.06, and while it’s sure to climb out of the red eventually, Miller’s already established himself as one of baseball’s most electric pitchers.
3. Wilyer Abreu, OF, Boston Red Sox
Abreu earned himself a late August call-up in 2023 but retained his rookie status coming into ‘24. He hit well in his debut, and has built on last year’s showing to quickly become one of Boston’s most important pieces so far.
Abreu ranks fourth among AL rookies in runs scored (16) and RBIs (13), adding strong defense in right field and speed on the base paths, going a perfect 5-for-5 in stolen base attempts. If there’s a reason to temper optimism a bit, it’s the fact that his .297/.381/.473 slash line is buoyed by a .403 BABIP. Statcast paints a far less enthusiastic view of Abreu, with an expected batting average of .225. Even if regression is on the way, he’s shown enough to solidify promise as a bonafide everyday player.
Gil gave up just two hits and no runs with five strikeouts in his last start against the Orioles.
Tommy Gilligan-USA TODAY Sports
4. Luis Gil, SP, New York Yankees
New York’s rotation has collectively risen to the occasion in reigning Cy Young Award winner Gerrit Cole’s absence, and Gil has more than done his part in the efforts.
The 25-year-old has allowed two runs or fewer in four of his six starts. His most impressive outing was also his most recent: 6 1/3 shutout innings against the Orioles on Wednesday. Gil averages 11.61 strikeouts per nine innings, fourth-most among pitchers who have thrown at least 30 frames. Walks have been an issue, though one that’s trending in the right direction: He gave up 17 free passes in 19 2/3 innings in his first four outings, but has allowed only three in his last two starts.
5. James McArthur, RP, Kansas City Royals
A Royals team coming off of a 106-loss campaign has been one of 2024’s biggest surprises so far, with a 20–15 record and the second-highest run differential (plus-44) in the AL. There’s plenty of credit to go around the roster, but McArthur’s emergence as a lockdown closer (Sunday’s blown save against the Rangers notwithstanding) deserves recognition.
McArthur’s best asset is his control. He’s walked only two of the 66 batters he’s faced so far, compared to 18 strikeouts. Missing bats is also a strength, as McArthur has a whiff rate of 34.9%. Sunday’s meltdown was his first blown save since taking over as the team’s closer, but even then, his strengths were on display. He drew 18 swings on his 30 pitches—with eight of them whiffs—and he didn’t walk a batter. McArthur spent six years in the Philadelphia Phillies’ system working primarily as a starter before being traded to the Royals in 2023, beginning his transition to the bullpen. He seems to have found his rhythm there, and has so far played a crucial role in one of MLB’s best success stories.
The Chicago White Sox are in the midst of a historic slump. And it doesn't appear to be getting better anytime soon.
The White Sox, who have lost a franchise-worst 14 straight games, were tied 1-1 with the Boston Red Sox in the third inning when left-handed pitcher Garrett Crochet made one of the oddest errors of the 2024 MLB season.
After fielding a soft ground ball hit by Jarren Duran that landed short of the mound, Crochet fired an errant throw past first baseman Andrew Vaughn. Vaughn raced after the ball, and Duran wheeled around first and second base and ended up at third.
The White Sox held a long meeting on the mound after the play. Once it concluded, Crotchet stepped off the mound to appeal that Duran didn't touch first base while rounding it on his way to second. But Crochet misfired—again—on his throw to first base, and Duran trotted home for the Red Sox's second run.
"That's what bad teams do," an analyst on the NESN broadcast said.
The White Sox have separated themselves as the worst team in baseball this season. Entering Friday, they had just 15 wins—seven fewer that the lowly Miami Marlins and Colorado Rockies—and rank last in batting average (.216) OPS (.618) and total runs scored (192).
Like race car drivers and opera singers, pitchers need to summon another gear in pivotal moments. It is how Jack Flaherty in 2019, at just 23 years old, joined Clayton Kershaw and Roger Clemens as the youngest pitchers in the past 48 years with a league-leading WHIP under 1.00. Averaging 93.8 mph with his heater, Flaherty, then with the St. Louis Cardinals, could hit 97 when he floored it.
The complement of two sharp breaking balls also made him the best young pitcher in the game. Riches and awards were to follow as surely as they did for Kershaw and Clemens.
His ascension never happened. The pandemic and injuries, especially to his oblique and shoulder, cast him into such a four-year wilderness of mediocrity (4.42 ERA) that when he hit free agency last winter at the prime age of 28, he could do no better than a one-year, $14 million prove-it flier with the Detroit Tigers.
That contract today looks like one of the best bargains of the winter. Jack is back. Entering a start Monday against the Cleveland Guardians, Flaherty leads the league in strikeouts, has posted a historic strikeout-to-walk rate to start a season, has tweaked his delivery and pitch usage and, yes, has rediscovered that extra oomph when he steps on the gas.
Look no further than the 1-and-2 fastball he threw to Lars Nootbar of the Cardinals in his last start Tuesday. Dotting the outside corner, the pitch was clocked at 97.8 miles per hour, as hard as Flaherty has thrown a baseball in five years.
“There were definitely times last year where I wanted to go to another gear and it was like it just stayed the same,” Flaherty says in a conversation I had with him earlier this year. “It was weird, and it just wasn't there, for whatever reason. And this year when I want to go to another gear, I’ve been able to get there.”
Says Tigers manager A.J. Hinch, “He was electric in his last start. He can really miss bats with his two breaking balls. His fastball was special the other day.”
Flaherty tied an American League record by striking out the first seven batters he faced in that game against his former team. He tied a career high and an MLB season high with 14 strikeouts overall. His average fastball velocity was 95.1, the fourth highest game average of his career and his best in four years. He obtained 24 swinging strikes, one short of his career high set in 2018. Ten of those whiffs came on his fastball, tying a career high.
The rebuilding of Flaherty began as a free agent after last season, which included telephone conversations with Tigers pitching coach Chris Fetter and assistant pitching coaches Robin Lund and Juan Nieves. They noticed his fastball properties improved after his Aug. 1 trade to the Baltimore Orioles, though his ERA in nine games with Baltimore was 6.75.
“I didn't feel great and by the end, it was just, ‘How can I get outs?’ “ Flaherty says. “Regardless of how it feels and whatnot, it's September. You’re put into a pennant chase. It was, ‘We'll just see. Find a way.’”
The Tigers’ coaches had success that year rebuilding another free agent pitcher, Michael Lorenzen, then 31. They de-emphasized his sinker in favor of more high-spin four-seamers. Lorenzen set career highs in wins, innings and strikeouts, made his first All-Star team and, after a trade to Philadelphia, threw a no-hitter. They had plans for Flaherty, but only hinted at them during the recruitment.
“When things were getting serious, we were on a call for two hours,” Flaherty says. “We talked this out. They presented ideas, but they don't want to … Those are tricky calls. They can't give you everything, like, ‘Here's all the secrets of what we think is going to make you better.’ But like, ‘You know, here's what we saw last year, and we can kind of help you get back.’ I've definitely never gone through it.
“Those calls are tricky because it's like, how do you ask them, ‘What can you do to help me?’ And then they give you a little bit, but not be able to give you everything because ‘If you don't sign here, we don't want to tell you this is what to do.’
“But in the end, it was their effort and the attention to detail that sold me.”
Flaherty pitches against the Minnesota Twins at Comerica Park on April 14.
Brian Bradshaw Sevald-USA TODAY Sports
Flaherty signed with Detroit on Dec. 20. Two weeks later, Frankie Montas, who is three years older than Flaherty and threw just 1 1/3 innings last season, signed with the Cincinnati Reds for $16 million, $2 million above Flaherty’s salary.
“Obviously it was a different offseason,” says Flaherty, who was a free agent for the first time. “At first it was not like having a team or anybody to go to and say, ‘Hey, what adjustments need to be made?’ So, I was kind of diving into it with my own team, my group, and figuring out, ‘What do we need to change?’ Because obviously, I was healthy, great, but I was not able to sustain success the way I wanted to. I didn't feel like the ball came out the same way. So, we had to dive into that and start making those adjustments.
“Once we signed here, then it was constant conversation [with the Detroit coaches]. ‘Okay, these are the adjustments that we think we can make.’ Now I had somebody to bounce ideas off of and go back and forth and send video to when it came time for a [bullpen]. So, it was a little bit more of, I kind of had to get back to a daily grind. Every day. And try to get back to the way I wanted my body to feel.”
Flaherty did not overhaul his delivery. He still has the smooth, old-school, three-part windup – hands over the head, kick and fire. He worked at fine-tuning the tempo and sequencing of that delivery. Ever since he starred on the mound and at shortstop for Harvard-Westlake High in California, Flaherty has been at his best when he relies on athleticism more so than pure mechanics. The injuries had compromised that athleticism.
“There were points last year where I just didn't … I tried as hard as I could to just be an athlete and for whatever reason it just felt weird,” he says. “I would say that I'm moving a lot better this year. Whether you want to call that mechanical? Sure. But I think the way that I'm going to fix it is the way I've moved, the stuff that works better for me. We really dove into the way that I was moving last year, and it would just be like, ‘Yeah, that's it!’”
An even bigger change came with how Flaherty used his pitches. Back in 2019, Flaherty threw fastballs 58.4% of the time. Since then, as analytics grew more sophisticated and technology around the game exploded, fastball use in MLB has declined every year—down to 46.7% this season, an all-time low.
The change was driven by a new generation of coaches, such as Fetter, who grew up with those modern tools. They know average spin is harder to hit than above-average velocity, and that the shape of spin can be custom designed. Fetter, 38, was hired by the Tigers after the 2020 season after serving as pitching coach for the University of Michigan. In a reversal of the historical paradigm, change flowed up to the majors from amateur baseball, including colleges and private instruction facilities.
Under Fetter, the Tigers have reduced their fastball use for a fourth straight year, ranking among the bottom 11 teams. Despite finding his turbo-boosted fastball again, Flaherty is throwing about as many fastballs as he did last year (43.7%), which is below major league average.
The biggest changes Flaherty has made under Fetter are ditching his ineffective cutter (.545 slugging percentage last year) and leaning much more on his swing-and-miss slider and curveball. He is throwing a career-high 52.6% breaking pitches, up from 44% last year and the fourth-most in MLB (min. 500 pitches). He has cut the batting average against his slider from .339 to .224 and his curveball has the third-most horizontal movement in MLB (min. 100 curves).
Pitchers who trade fastballs for spin often do so at the cost of more walks. Not Flaherty. He became only the seventh pitcher with 50 strikeouts and no more than five walks through the month of April. Even allowing that the modern era features more games in April, he joined a very impressive group:
Sure, it’s only six starts. And Flaherty hasn’t thrown 150 innings in a season since his breakout year of 2019. But one month into this season, the baseball is jumping out of Flaherty’s hand again. The athletic feel in his delivery has returned. So has 97 when he steps on the gas. It took an entire winter, when a 28-year-old free agent starter could do no better than a one-year deal, to bring back Jack.
“There’s working hard,” he says about his way back, “and then there's also being super intentional about it.”
