Pittsburgh Pirates’ veteran right-hander Mitch Keller hasn’t produced like his normal self in 2026. He has mostly served as a solid, league-average rotation anchor over the last four seasons, but currently has a 5.02 ERA, 4.39 FIP, and 1.31 WHIP over 100.1 innings pitched. Keller is striking out batters at a career-low rate, with a 17.3% K%, and his 7.7% walk rate is his highest single-season mark since 2022. However, there is one change Keller can make that would likely help him rebound dramatically.
Most of Keller’s struggles this year have come against left-handed batters. Right-handers have given him zero trouble in 2026. They’re batting .204/.294/.282 with a .267 wOBA against Keller. He has a respectable whiff rate, inducing a whiff% of 24.4% against right-handed hitters. However, he excels at limiting quality contact, holding them to a strong 3.6% barrel rate.
The story is a lot different vs lefty batters, however. They are hitting .283/.340/.492 with a .359 wOBA against Keller. His 16% K% vs lefties is the lowest mark of his career thus far. It is also the worst lefties have hit Keller since 2021 based on wOBA. Keller induces far fewer swings and misses against lefty batters, with a 17.7% whiff rate. They also make far more quality contact against Keller, with a 9.6% barrel rate.
So what can Keller do to fix this? The simple fix may be to drop his cutter again. Keller brought his cutter back and is using it 7.1% of the time this season. Most of that has come against lefty batters. About 10% of the pitches he throws to lefties are cutters. Unfortunately, Keller’s cutter has never been a quality pitch.
Keller first started throwing a cutter in 2023. Between ‘23 and ‘24, opposing hitters batted .292 with a .521 slugging percentage against the pitch. They only whiffed in 22.5% of their swings against his cutter. With how poorly the pitch performed, Keller pretty much shelved the pitch in 2025. He threw just three cutters all year last season, all of which came in just a single game against one batter. Ironically, that batter, Alec Burleson, hit a double against Keller while using his cutter.
This change occurred sometime in May. Keller only used his cutter 3.8% of the time in April. Since then, he has used it about 8.5% of the time. April is also Keller’s best month by far. He finished out the first month of the season with a 3.18 ERA, 3.09 FIP, and 1.15 WHIP. He induced plenty of soft contact as well, with an 86.5 MPH exit velocity and a 3% barrel rate. While he still carried a 3.70 FIP in May, his ERA spiked to 5.50, and batters were hitting him far harder, with an 89.2 MPH EV and an 8.5% barrel rate. Things have only progressively gotten worse, as he has a 6.47 ERA, 6.53 FIP, 91.2 MPH EV, and 10.2% barrel% since the start of June.
The pitch is once again giving Keller trouble in 2026. He has used his cutter in parts of 28 different plate appearances. In those 28 plate appearances, he has given up eight hits, including three doubles and a home run, and has induced just two strikeouts. Seven of those eight hits were lefty batters. He is allowing far less hard contact with his cutter this time around, holding batters to an 81.8 MPH exit velocity. However, introducing a seventh pitch to his arsenal, especially a pitch that he struggled with in years prior, may be affecting not just his ability to get lefty batters out, but also how he sequences against righty batters as well.
Keller already has six other pitches that aren’t his cutter. All but one of the six other pitches has induced a wOBA below .320 this year, and his cutter has the lowest put-away percentage of any of his seven offerings. Something has to change, and Keller dropping his cutter again might be the easiest solution. It’s a pitch that has given him trouble year-after-year, and his best month of 2026 so far was when he was using it less than 5% of the time. Lefty batters have had no problems seeing it, and with how much he has struggled against them, he should change his approach and leave the cutter behind.
