Whenever a pitcher joins a new organization, the question is about what kind of tweaks the organization can make to the player’s arsenal. It might be with adding a new pitch. The Phillies traded for Jesus
Luzardo and gave him a sweeper that changed his career. Clay Holmes added a kick-change with the New York Mets last season when he converted to the starting rotation.
For Brad Keller and the Phillies, potential changes are likely going to be eye-popping. Keller already throws five very good pitches as a one-inning reliever, so there isn’t a major need to add or subtract any shapes.
There are still ways to play with a pitcher’s mix, as the Boston Red Sox acquired Garrett Crochet and made mostly minor adjustments, except for usage. He went from throwing 55% four-seam fastballs in 2024 to 36% in 2025. Boston had him throwing a lot more sinkers and a few more sweepers instead.
The Phillies might have some subtle tweaks in mind to make Brad Keller even better than last year. Let’s look into how he faces right-handed and left-handed hitters to try and figure out what possible changes Caleb Cotham and the coaching staff could make.
Right-Handed Hitter Approach
2025:
- 31% Four-seam fastball
- 26% Sinker
- 24% Sweeper
- 18% Slider
- 1% Changeup
The first change the Phillies might make is to change how he uses his four-seam fastball and sinker. From 2022-2024, the Phillies ranked 5th in right-handed sinkers against right-handed batters last season. They backed off that usage in 2025, but some of that was due to personnel. Zack Wheeler and Aaron Nola made 41 combined starts in 2025 and most of their bullpen righties did not carry sinkers (with Orion Kerkering being an obvious exception).
There is still enough evidence during Cotham’s tenure as pitching coach to think the Phillies want to keep up with platoon-based pitching so Keller could raise his sinker usage while throwing less four-seam fastballs.
His sinker also just plays a lot better against right-handed hitters compared to his four-seam fastball. Right-handed hitters hit .219 with a .344 slug against his four-seam last season. Were those numbers good? No but there is a better alternative.
Right-handed hitters hit just .147 without an extra base hit against his sinker last season. Keller gave hitters uncomfortable swings with an average launch angle allowed of -16. He also had a 9% whiff rate increase when throwing that pitch compared to his four-seam.
That’s a lot of numbers but based on the results from last year, it all proves that Keller’s primary fastball to right handed hitters should be with his sinker and not his four-seam fastball.
Left-Handed Hitter Approach
2025:
- 57% Four-seam fastball
- 25% Changeup
- 16% Slider
- 2% Sweeper
- <1% Sinker
Coming up with these changes are going to be based less on the philosophical approach the Phillies have and more on what Keller does well. This is partially because we don’t know what the Phillies would do with a pitcher like him.
2024 Jeff Hoffman might offer the closest comparison with a full season’s worth of data. He threw 41% four-seam fastballs, 33% sliders, and 26% splitters to left-handed hitters that season.
However, I wouldn’t predict the Phillies to raise Keller’s slider usage to left-handed hitters. In part, because it’s just not a good idea to throw down and in against left-handed hitters a lot and the Phillies don’t carry a philosophy that asks pitchers to do that.
From a general usage standpoint, the Phillies likely lower Keller’s four-seam usage for more changeups but I think there is something more underlying that could help him unlock more strikeouts against southpaw hitters.
His two-strike usage seems a little jarring to lefties:
- 69 four-seam fastballs
- 48 changeups
- 32 sliders
This is where Cotham and the staff should boost his changeup usage. Southpaws hit just .171 with a .200 slug and a 39.4% whiff rate against his changeup overall last year. That should be his primary two-strike pitch to left-handed hitters.
Neither his slider nor his four-seam fastball gets enough whiffs to warrant that kind of two-strike usage so attacking with more changeups in those situations feels like an easy fix to make.
There feels like some meat is still left on the bone with Keller as a late-inning reliever, and this is coming off a 2025 where he finished 15th in ERA, 34th in fWAR, and 31st in FIP among relievers. The Phillies could help him go from a very good setup man to being just one of the ten best right-handed relievers in the sport next season.
