Will the Red Sox Throw the Fewest Fastballs Again in 2025?

During the 2024 season, the Red Sox didn’t just throw the fewest fastballs in the league; they came in last by a lot. Four-seamers and sinkers made up just 36.9% of Boston’s pitches. That was more than 10 percentage points below the league average of 47.7%. No other team was below 42%, and 10 different teams were above 50%. Here’s what that looks like on a bar graph. The Red Sox are the red bar at the very end.

I feel like that graph doesn’t really do just to how much of an outlier the Red Sox really were, so instead of using a baseline of zero, I’m going to show you the same graph, but this time the X axis is set at the league average of 47.7%.

Does that make it clearer? Only one other team in baseball, the Twins, was more than five percentage points away from the league average. The Red Sox were more than twice as far away as the Twins were. They were in their own galaxy.

As you surely know, the league has been moving away from leading with the fastball for decades now. In 2009, 58.4% of all pitches were four-seamer or sinkers (coincidentally, the Red Sox still ranked last, at 46.7%). Teams are encouraging their pitchers to throw their best pitch more often, and in 2024, the Red Sox decided to jump out in front of the rest of the league. The data only goes back to 2002, but it's very safe to say that the 2024 Red Sox ran the lowest fastball rate in major league history.

You’d be hard-pressed to argue that it didn’t work. In 2023, they ran a 4.52 ERA and 4.23 xFIP, which ranked 21st and 15th, respectively. In 2024, those numbers were 4.05 and 4.03, which ranked 16th and 12th. In other words, the Red Sox improved significantly in ERA, while an advanced ERA predictor credited them with a smaller improvement. Obviously, there’s always going to be year-to-year variation, so while one season is probably too small a sample size for us to declare victory, at the very least, we can say that this focus hasn’t hurt.

There’s no reason to expect the Red Sox to change their approach in 2025. However, over the offseason, they added some pitchers who rely pretty heavily on fastballs. Garrett Crochet threw his fastball 55.8% of the time in 2024. Aroldis Chapman was at 61.4%, and Justin Wilson was at 49.5%. The Red Sox will also be getting Liam Hendriks back, and he threw his fastball 58.6% of the time in 2023. Knowing all this, I got curious about whether we should still expect Boston to run the lowest fastball rate in the league next season, so I crunched the numbers. I pulled depth charts projections from FanGraphs, which broke down how many innings each pitcher on the team might expect to get, then I pulled their fastball rates from 2024. For players who missed the 2024 season like Hendriks or Lucas Giolito, I pulled rates from 2023. For players who haven’t yet appeared in the majors, I pulled their fastball rate from the minors.

In order to calculate the team’s overall projected fastball rate, I simply made each player’s rate proportional to their percentage of the team’s innings total (so, for example, Justin Slaten’s 66 projected innings are weighted twice as heavily Cooper Criswell’s 33). This is a very rough way to calculate things, but it’s good enough for our purposes and it left me with a 42.7% fastball rate. To be clear, I still expect the Red Sox to come in a bit lower than that rate for a couple reasons. First, the league fastball rate drops every year, so we should probably expect a small drop from every team. We might even expect that drop to accelerate after the rest of the league saw the Red Sox succeed by going all-in on this approach. Second, all of those new roster additions who throw lots of fastballs? We should probably expect them to stop throwing them so often, simply because they joined the Red Sox: The Team That Doesn’t Throw Fastballs. Regardless, that’s a huge increase from 36.9%. We should definitely expect the Red Sox to throw more fastballs this year.

Back to our original question: Will they still be last in the league? In 2024, a 42.7% fastball rate would have finished 29th in the league, just ahead of the Twins at 42.4%. If, as we expect, the Red Sox do push some of their new additions away from their fastballs, the Red Sox should retain their crown as the sovereigns of soft stuff. All the same, we should probably expect the contest to be a bit closer than it was last season.