Ahead of the MLB All-Star Game in Atlanta last month, Detroit Tigers ace Tarik Skubal looked around the clubhouse and noticed something strange.
“There were a ton of lefties,” Skubal said.
Lefties tend to spot any lefties in their orbit, and so Garrett Crochet, the Boston Red Sox lefty dueling Skubal for a Cy Young award, saw it too. At this year’s Midsummer Classic, the left-handed starters outnumbered the righties. “That’s crazy,” Crochet said. Other worthy lefties were snubbed, he added, such as Philadelphia’s Cristopher Sánchez and Ranger Suárez.
Now the rest of the industry is noticing: We may be witnessing a zenith of left-handed pitching. In 2025, lefties have a collective 3.73 ERA. Righties? 4.30. It’s the greatest gulf between them since ERA became an official stat in 1913.
Despite comprising only a quarter of the major league pitching population, left-handers account for five of the top seven qualified starters by ERA, and 11 of the top 23. By adjusted ERA, this is the most dominant left-handed season in the modern era — and it’s not particularly close.
MLB ERA leaders
Rank
Player
Team
Hand
IP
ERA
1
PIT
RHP
154
2.16
2
CIN
LHP
130
2.28
3
DET
LHP
159.1
2.32
4
HOU
RHP
149
2.36
5
BOS
LHP
159.1
2.43
6
PHI
LHP
157
2.46
7
CHC
LHP
148
2.61
“In the American League, all the Cy Young guys are lefty,” Kansas City Royals first baseman Vinnie Pasquantino said. Over in the National League, San Diego Padres infielder Jake Cronenworth remarked, each division has several outstanding lefties. “There’s not only more of them,” Cronenworth said, “but they’re becoming extremely dominant.”
“It’s insane,” Pasquantino said. “And they all throw hard as f— now.”
Historically, left-handed pitchers have fared slightly better than righties, but there’s been balance for much of the modern era. In the past 40 years, righties had a better cumulative ERA 20 times, and lefties 20 times, never separated by more than two-tenths of a run. So how is it now that a sudden southpaw surge has overwhelmed the sport? And is it here to stay?
Largest ERA gaps
RankYearRHP ERALHP ERADIFF
1
2025
4.30
3.73
0.57
2
1924
4.16
3.74
0.42
3
1949
4.27
3.85
0.42
4
1913
3.17
2.79
0.38
5
1916
2.83
2.47
0.36
6
1953
4.25
3.89
0.36
7
1992
3.65
3.97
0.24
8
1975
3.79
3.55
0.32
9
1942
3.49
3.72
0.23
10
1961
4.09
3.87
0.22
Explaining how lefties are doing this requires plumbing statistical archives, parsing splits, gathering theories from players and puzzling over them with evaluators and pitching savants. It takes many ingredients to create such an outlier season, but the factor cited first in almost every conversation on the topic is …
Reason 1: A lack of exposure
In 2023, his breakout season in the minors, Red Sox outfielder Roman Anthony knew his overall numbers were obscuring his struggles against left-handed pitching. Anthony, a left-handed hitter, was named Boston’s minor league hitter of the year while batting .219 against lefties.
“Luckily,” he said, “90 percent of the guys I faced were right-handed.”
That offseason, Anthony trained against lefty big leaguers, minor leaguers, batting practice throwers and angled pitching machines. “Making the practice environment as impossible as I can — and failing most of the time in my practice — so that now the average left-handed pitcher looks pretty stock,” he said. Anthony hit .316 against lefties the next season. Still, he said, “at the end of the day, a machine can only get you so ready to go out in front of 40,000 people and face the best left-handed pitcher in the game.”
Hitters get far fewer reps against lefties. Always have. Always will. About 10 percent of the world’s population is left-handed. Hitters rarely face lefties growing up. They scarcely see good lefties early in pro ball. “They go quick through the minors,” Royals star Bobby Witt Jr. said. In the Red Sox clubhouse, Anthony gestured to Crochet. You don’t really see those guys in Triple A. Crochet bypassed the minors entirely.
“I like facing lefties,” Witt said. “But you just don’t see it as much.”
The number of left-handed pitchers in the majors has dwindled over the past five years, and the proportion of games started by left-handers has dropped from 31.9 percent in 2021 to 26.2 percent in 2025. Padres outfielder Fernando Tatis Jr. said hitters are simultaneously seeing fewer lefties and higher-caliber ones — many of them aces or No. 2 starters.
Tatis had at least a .915 OPS against lefties in his first three full seasons in San Diego. The past two years, it’s been below .690. Tatis said lefties are throwing him pitches with “more angle, more cut” this season, but that’s not what he believes is the root of his issues: “(It’s) probably because 80 percent of the time I’m facing righties, you know?”
But the exposure argument doesn’t explain lefties’ superiority in 2025 specifically as much as the fact that …
Reason 2: Lefties can’t hit lefties
Pasquantino’s dad, Dennis, doesn’t get it.
“It makes him so upset,” Pasquantino said. “He’s like, ‘Why? Why? I don’t understand!’
“I’m like, ‘I don’t know. It just is.’”
No matchup has a hitter at a more stark statistical disadvantage than left-on-left.
OPS against right-handed pitchers: .748
OPS against left-handed pitchers: .658
LHH OPS splits since 2021
Year
vs RHP
vs LHP
DIFF
2021
.741
.656
.085
2022
.708
.647
.061
2023
.753
.690
.063
2024
.733
.668
.065
2025
.748
.658
.090
This is why managers stack their lineup with right-handed hitters against lefties, and why pitchers notice when they don’t: “Kris Bubic says it all the time: ‘Ooh, I got three lefties in the lineup today. I’m not used to that,’” Royals pitching coach Brian Sweeney said. Lefty starters face vastly different lineups than their right-handed counterparts, as right-handed platoon bats replace lefties — often even stars — either to give them rest or spare them the indignity of televised left-on-left torment.
A slugging lefty, Pasquantino’s career OPS against right-handers is more than 100 points higher than against left-handers. This is not a point of pride. He wants to be entrusted to do damage against both hands, as he did last week with a laser home run off Washington Nationals lefty Mitchell Parker.
“It doesn’t make the at-bats mean more,” Pasquantino said. “But I also want to prove I can hit lefties.”
More and more lately across the league, one pitch is preventing that.
“The sinker,” Pasquantino said.
“The sinker’s coming back in play,” New York Mets pitching coach Jeremy Hefner said.
LHP usage vs. LHH
Year
FOUR-SEAM
SINKER
SLIDER
SWEEPER
2021
35.8%
18.3%
22.2%
3.0%
2022
32.4%
20.3%
22.4%
5.6%
2023
30.1%
22.0%
20.5%
9.4%
2024
29.1%
24.9%
19.1%
10.0%
2025
26.6%
25.1%
21.9%
10.6%
Historically, the book on left-on-left was four-seamers away and breaking balls. Last week, Pasquantino was surprised to step in against Red Sox closer Aroldis Chapman and see the hardest-throwing lefty in the sport dot three consecutive sinkers at the bottom of the strike zone. The next night, Pasquantino’s Royals were folded by Crochet, whose primary pitch to left-handed hitters is a sinker he’s been throwing for less than a year. It’s a 96 mph buzzsaw lefties have yet to hit for extra bases.
“I feel like it’s not even the great equalizer,” Crochet said, grinning. “It feels like it’s the great decimator.”
In an opposite-handed at-bat, pitchers typically have one extra pitch at their disposal. (For lefties, a changeup.) Despite being a pitch short against lefty hitters, Crochet said, “You really don’t need the extra pitch when you have the sinker boring in on them.”
The Phillies’ Kyle Schwarber has reverse splits this season, with a .978 OPS against lefties and a .924 OPS against righties. For opposing managers, it’s “pick your poison” with Schwarber, teammate Bryce Harper said. On Friday, Schwarber was hitless in three at-bats against Nationals lefty MacKenzie Gore and out of sync until adjusting his setup midgame. Later, the Nationals went to another lefty, Konnor Pilkington, in a tied game. Pilkington hung a slider. Schwarber smashed his 17th homer this season against a lefty; no other lefty hitter has more than 10.
Schwarber’s key to the left-on-left quandary: “Working on the mentality of it just being an at-bat.”
It’s easy to see why avoiding left-on-left at almost all costs is an attractive option for major league clubs. But some players ask: If lefty hitters get so few opportunities to face lefties these days, how can anyone accurately assess their (in)ability to hit same-sided pitching? Imagine going a week without facing a lefty, Royals infielder Adam Frazier said, “then you’re sitting on the bench and have to pinch-hit against a lefty reliever throwing 98 mph sinkers. Good luck.”
But we may be focusing on the wrong matchup. Left-on-left numbers are always bad. They were worse a decade ago. What has changed dramatically this season is that …
Reason 3: Righty hitters can’t hit lefties
This year, the platoon advantage has all but vanished for right-handed hitters.
OPS against right-handed pitchers: .707
OPS against left-handed pitchers: .716
That delta is less than half the difference in any of the previous 20 seasons.
RHH OPS splits since 2021
Year
vs RHP
vs LHP
DIFF
2021
.711
.766
.055
2022
.700
.736
.036
2023
.714
.760
.046
2024
.692
.728
.036
2025
.707
.716
.009
According to the hitters trying to turn around this trend, the change this season — right-handed hitters have a below-average wRC+ against lefties for the first time since 2004 — is all about location.
Red Sox third baseman Alex Bregman said that early on in his career, lefties attacked with fastballs and changeups away. Now they’re coming up and in. “Really good four-seam fastballs in,” Bregman said. “They’re getting it there, and they’re throwing it harder than ever.” Lefties are also more confident dropping back-foot sliders, added Red Sox outfielder Rob Refsnyder. For right-handed hitters trained to drive a pitch from a lefty to right-center field, facing a crossfire pitcher throwing inside has a handcuffing effect. And when they still want to attack the outer edge, several top lefties, like Skubal and Sánchez, have outlier changeups that grade among the best pitches in the sport.
Left-handed pitchers operate at a platoon disadvantage over 70 percent of the time, far more than their right-handed counterparts (49 percent). When MLB instituted a three-batter minimum in 2020, lefty specialists were weeded out, and those who remained had to learn to retire righties.
“You want to be really good or elite on the same side, but you want to be able to get the other guys out,” said Mets All-Star left-hander David Peterson. “For me, as a starter, the only way I’m going to be able to get deep into games and have more trust to go further through the lineup a couple times is showing you can get righties out.”
While lefties can often subdue same-handed hitters simply by attacking with their strengths, it takes creativity to solve the opposite-handed hitter. With lefty Evan Sisk (recently traded to the Pittsburgh Pirates) struggling against righties, Sweeney told him his primary pitch, a sinker, would work maybe once per at-bat. He had Sisk throw more four-seamers and add a cutter. “Building a repertoire to get righties out is definitely a focus,” Sweeney said.
The process of refining a pitcher’s arsenal is more streamlined than ever, thanks to how technology and training have shaped …
Reason 4: The evolution of the “soft-tossing” lefty
This spring, pitching analyst Lance Brozdowski predicted that the average number of pitch types thrown by a starting pitcher, a figure climbing steadily in recent years, would eclipse five for the first time in the pitch-tracking era.
“That was my take,” Brozdowski said last week, “that mix diversity would take over.”
The current average: 4.96 pitch types per starter. That rise has been propelled in no small part by left-handers, as they have collectively added a full pitch to their arsenal in five years, from 3.85 in 2021 to 4.79 in 2025.
“Pretty much every lefty starter now is really, really nasty,” Refsnyder said, “or working on something to get there.”
Pitch types thrown per starting pitcher
Year
RHP
LHP
MLB AVG
2021
4.58
3.85
4.32
2022
4.43
4.04
4.32
2023
4.68
4.08
4.53
2024
4.91
4.22
4.73
2025
5.03
4.79
4.96
Minimum 2,000 total pitches and 100 per pitch type; 2020 and 2025 prorated
Back when Red Sox chief baseball officer Craig Breslow was a journeyman lefty reliever, he threw almost exclusively sinkers and curveballs to lefties, and sinkers and changeups to righties. His heater averaged 90 mph. These days, that’s what Anthony might call a stock lefty. “Now we see left-handers with multiple fastballs and breaking balls,” Breslow said in an email, “and repertoires that are more difficult to defend against.”
As for why, Breslow said, it starts with how training methods have accelerated, helping boost velocity. The average lefty fastball (93 mph) is still almost two ticks slower than righties’ (94.8 mph), but only 12 MLB lefties this season have sub-90 mph average heaters, compared to 37 a decade ago.
Secondly, Breslow added, technology has transformed pitch design. With pitch-tracking data, slow-motion cameras and biometric data, pitchers have more information about themselves and about hitters. Peterson gave an example: “Say there are five percent more hitters who have a flatter bat path. As a lefty, if you can have a pitch or two that gets more depth, you can miss more barrels. You know what I’m saying?”
Mets outfielder Brandon Nimmo said the game is “so much more advanced now” than when he debuted in 2016, and nowhere is that clearer than in pitching approaches. Back then, pitchers had an attack plan against lefties and righties, but they both contained the same pitches. Now, pitchers are armed with diverse pitch mixes and individualized plans.
“They all have weapons to get at your weaknesses, and it all comes down to execution,” Nimmo said. He added, “We’ll start to see some young kids come up who have been exposed to this at an earlier age and it’ll be old hat. Then it will be the pitchers’ turn to do something.”
Until then, the arms have the upper hand. But what their evolution still can’t explain is why …
Reason 5: We still don’t understand what makes lefties good
How are lefties getting away with this? Compared to righties, they on average have less velocity, lower spin rates and fewer pitch types. They are almost always at a platoon disadvantage. And yet they’re outperforming right-handers.
“It is funny, when you say it that way,” Crochet said. “It’s hard to quantify.”
Harder than he knows. A 2020 study from Guy Molyneux and Phil Birnbaum concluded that lefties’ “hidden advantage” was due to hitters’ unfamiliarity with pitches from the left side, an effect similar to that studied in tennis, volleyball and soccer. The authors estimated that the lefty advantage was 0.6 runs allowed per nine innings.
More recently, while iterating with Stuff+, the pitch quality model he helped create, The Athletic’s Eno Sarris wrestled with why left-handed pitchers consistently outperformed the model’s predictions. It wasn’t until baking in extra credit for lefties — acknowledging that their stuff plays up from what their velocity and movement readings would indicate — that the model became adequately aligned with reality.
It’s a debate evaluators regularly have: Do lefties have an inherent advantage?
“Listen,” Brozdowski said. “Cristopher Sánchez is an incredibly simple pitcher if you look at him from a usage and maps standpoint. And that dude is unbelievable! I’m not entirely sure why.”
Both Sánchez and Houston Astros lefty Framber Valdez throw two pitches more than 70 percent of the time. That’s not the prototype of a modern ace. But here they are in the mix for a Cy Young.
Last week, the Cincinnati Reds and Phillies played a three-game series in which each game featured a left-handed starting pitcher with an ERA in the 2s in mid-August: Sánchez, Suárez and Cincinnati’s Andrew Abbott. “Those guys were gross,” Abbott said afterward. “And everybody’s different. It makes it kind of fun.”
For lefties, different is often described in one of a few ways: Funky, crafty, deceptive. None of those terms is easily quantifiable, though training facilities such as Driveline Baseball are studying the details that produce deception. Perhaps one day we’ll discover that the left-hander’s advantage is hidden in all sorts of biometric minutiae like lower release points, stride direction and placement on the rubber.
For now, maybe it’s this simple: They’re good because they’re good.
“Just look at their stuff,” Skubal said. “It doesn’t matter what hand you are if you have the stuff those lefties have.”
Growing up, Skubal was the only lefty thrower in his family. His 1-year-old son, Kasen, has started swinging left-handed, but often transfers objects to his right hand before throwing them. “Would I love for him to be left-handed? Sure,” Skubal said. “But I don’t really care what he does.” Even so, when Skubal, the best lefty in baseball, hands something to his son to throw, he places it in the boy’s left hand. It’s worth trying.
— The Athletic’s Cody Stavenhagen, Dennis Lin, Tim Britton, Chad Jennings, Charlotte Varnes and C. Trent Rosecrans contributed to this report.
(Illustration: Demetrius Robinson / The Athletic; Photos: Caean Couto, Jason Mowry, Alika Jenner / Getty Images)