Jameson Taillon, Left-Handed Batters, and the 2024 Chicago Cubs Rotation

In retrospect, Jameson Taillon’s first season in a Chicago Cubs uniform almost went exactly as expected. His 4.84 ERA is a pretty big jump from his 4.00 mark for his career, but the gap isn’t yawning, at least given the fickle nature of pitchers. He still managed to throw 154 ⅓ innings, a good total in the current era wherein pitchers are much more often deployed in shorter bursts.

Sure, his 1.6 FanGraphs WAR is his lowest total in any season in which he has thrown at least 100 innings. Yet, he averaged just 2.1 Fangraphs WAR over his two seasons with the Yankees. So while Taillon sure didn’t impress many in Chicago in his first year with the team, he proved himself to be a reliable back-end starter, even in a down year. What can we expect from him going forward?

The veteran righthander’s poor performance in 2023 can be chalked up to one thing: his results against left-handed hitters. Lefties hammered out a .363 wOBA against Taillon in 2023, according to FanGraphs. For reference, a .320 wOBA is considered average, and Austin Riley posted a .363 wOBA last year. Essentially, every left-handed hitter that stepped into the box against Taillon last year was as productive as Riley. 

That was a surprising problem, because Taillon was roughly split-neutral in his two seasons prior to joining the Cubs. In 2021, lefties had a .316 wOBA against him, while righties were at .304. In 2022, lefties were at .309 and righties .307. In no way was this a predictable issue for a typically steady starting pitcher.

Taillon’s season was also a tale of two halves. His first half was disastrous, as he had a 6.15 ERA heading into the All-Star break. His second half was miles better, as he posted a 3.70 ERA to close the season. Again, this change in performance can be attributed to how he pitched against left-handed hitters: In the first half, they had a .420 wOBA (equivalent to Corey Seager) against him. In the second half, it was a much more playable .308 wOBA (approximately Miguel Amaya). What was different?

To understand this, let’s go back to the 2022 season, when Taillon posted a career-best .309 wOBA against lefties. That season, he started throwing a cutter. He threw it 13.3 percent of the time against opposite-handed hitters, with great results: a .303 wOBA against, with only a 76.8 MPH exit velocity on balls in play to back that up, according to Baseball Savant. He attacked lefties with fastballs up and in, cutters in on the hands, curveballs down in the zone, and changeups away.

In 2023, Taillon doubled down on the cutter usage, throwing it 21.8 percent of the time against lefties. The changeup was almost completely scrapped, as he threw it only 5.9 percent of the time, down from 17.3 percent of the time in 2022. Cliffs notes: he went from throwing four pitches against lefties in 2022, to only three pitches in 2023. And it turns out his cutter got absolutely crushed: left-handed hitters put up a .450 wOBA against his cutter in 2023. 

Coming back to Taillon’s Jekyll-and-Hyde first and second half performances this past season, and remembering what we now know about how he attacked lefties in his successful 2022 campaign (fastball up and in, cutter in, curveball down), here were his fastball locations to lefties in the first half of 2023:

That is all over the place, to put it nicely. And here are the locations of his cutters before the break:

Interesting! This looks to me like Taillon was throwing his cutter exactly where he wanted to. It was the fastball over which he had no control. What makes a cutter good, and split-neutral, is how it plays off of a fastball. It looks like a fastball just long enough, until it breaks a little bit down and to the pitcher’s glove side. In this case, because he wasn’t controlling the fastball, they likely never looked similar enough, causing the cutter to get hit as hard as it did. 

Now, let’s see how his fastball location changed in his much more successful second half:

Much more consistent! Though at the same time, he wasn’t throwing it up and in like he did in 2022. What about his cutter location in the second half?

Oh! So Taillon completely changed his approach with his cutter from the first half of the season to the second half. Instead of attacking hitters inside with both pitches, he started trying to attack them away and off of the plate. While he did perform significantly better against lefties as a result, what is interesting is that he still gave up a .393 wOBA against lefties on fastballs and cutters in the second half. That was down from .468 in the first half, but the exit velocities and launch angles of the balls that were put in play suggest that the batted-ball results were roughly the same.

It was actually Taillon’s curveball that carried him in the second-half against players with the platoon advantage: they hit for just a .186 wOBA and had a 31-percent strikeout rate against the pitch. Those numbers were significantly better than the .344 wOBA and 24.4-percent strikeout rate that lefties had against the curveball in the first half. 

A curveball coming in from a right-handed pitcher is going to start up and away to a lefty, so my theory on this is that hitters found the curveball much harder to identify when it was paired with both the fastball and the cutter on the outside half of the plate. I also think it’s possible there’s some sample-size theater going on here: Taillon’s first-half FIP of 4.90 is not too far off of his second-half mark of 4.36, suggesting that the performance gap between the two halves was not as wide as the ERA would indicate.

What does this all mean for Taillon in 2024? I’d wager that his approach to lefties was a big focus for him during this offseason. When he takes the mound, pay close attention to it. Will he bring his changeup back? Where is he going to try to locate his cutter and his fastball? It all very well may determine if the remainder of his contract is looked at as a bust, or a solid investment.