Article: Three Things I’ve Noticed About Tanner Houck’s Rough Start

[Alex Mayes]

Tanner Houck has looked like a different pitcher in 2025, and not for the better. Three main things have stood out to me in both his outings so far. 

The Red Sox hoped that Tanner Houck would pitch like the guy who earned an All-Star selection in 2024. So far, after only two regular season starts, it has looked like last season may be an outlier. This drastic decline, which started during spring training, got me to wondering what could be going on with Houck and whether there was something he could do to try and rebound quicker.

I’d noticed a few things in both starts that I thought were interesting. First, his pitch mix is slightly different this season. Last year, he scrapped his four-seam fastball entirely and replaced it briefly with a cutter. He has brought his four-seamer back for 2025 and so far hasn’t thrown a cutter yet. Second, his sweeper seemed to be breaking much less than it did last year. His splitter was being thrown a tick harder than last year, but since he throws it mostly in the same location as his sinker, it doesn’t play off nearly as well with that increase in velocity.

It’s no secret that last season, the Red Sox were a fastball-light organization. Houck was arguably the biggest beneficiary of this, leaning heavily on a sweeper that kept hitters from both sides of the plate off balance. He’s still leaning on that sweeper, but so far he’s thrown his four-seam fastball 9% of the time, way more than the 1% of the time he used the cutter last year. The four-seamer has taken away usage on his best two pitches, the sweeper and the sinker. Last year, Houck used those pitches to keep batters on their toes, often swinging over the sinker and flailing wildly at a sweeper they had no chance to make contact with. So far this year, the sinker doesn’t sink like it did last year and the sweeper doesn’t sweep as much, forcing Houck to rely on a fastball back that lives high in the zone. A refocus on his top two pitches could go a long way towards getting Houck back to what he showed he could be last season.

Unfortunately, there's a problem with the sweeper. Even fans watching on television can tell that it’s not sweeping like it was when he was dominant. Last year, his sweeper had 16.7 inches of horizontal break. Hitters typically swung wildly at a pitch that ended up far out of the zone. This season though, the horizontal break is 14.2 inches, a full two and a half inches less break. That may not sound like a lot, but it can make a big difference. Moreover, Houck isn't locating the pitch like he did last season. In the heat maps below, 2024 is on the left and 2025 is on the right. 

Last season, Houck mainly used the pitch on his arm-side, throwing it as a front-door pitch to righties and a backdoor pitch to lefties. This season he's leaving the sweeper out ove the plate, allowing righties to get their arms extended. Houck’s arm angle hasn’t changed , so that’s not the reason why his sweeper isn’t moving like it should. There’s also not a giant difference in velocity, last season the sweeper came in at 83.2 mph while it comes in this season at 83.6 mph. There could be some correlation with that slight velocity increase, but it shouldn’t take over two inches of break off of a pitch.

That brings us to the slight uptick in velocity for the splitter. Last season, Houck threw his splitter at an average of 88.4 mph. So far this season, he’s averaging 89.5 mph. He mentioned in an interview after his final spring training start that he’s ready for the season and his "velo is up," but I think this slight increase is one reason why we’re seeing him get knocked around so much this season. His splitter and his sinker share tunnel off one another, keeping hitters behind on the sinker and out in front of the splitter. However, without as much velocity separation, hitters don't have to guess which pitch is which as often as they did last year. This means the hitter can sit on pitches on one side of the plate, ignoring anything else.

I understand that we’re working with a small sample size at this point in the season, and maybe I’m reading too much into things right now. That’s possible, but Houck has looked rough through all of spring training and the regular season, and these three things have stood out to me in both regular season outings so far. It’s entirely possible that Houck gets it together and changes the outlook on his season. As it currently stands, though, the number two starter role could be up for grabs, and there are a number of pitchers behind him looking to move up in the pecking order.

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