Tanner Houck’s slider could be MLB’s next great pitch

Young prospect Tanner Houck flashed his brilliance on the mound for an otherwise dismal Boston Red Sox pitching staff in 2020.

The Boston Red Sox’s pitching in the pandemic-shortened season was, to put it mildly, disgraceful. Their pitching staff was the only group in baseball to post negative value by wins above replacement, clocking in at -0.2 fWAR. They also allowed a league-high 1.68 HR/9, and their collective 5.58 ERA was only narrowly better than those of the Colorado Rockies (5.59) and the Detroit Tigers (5.63). By all accounts, it was a pitiful display.

But amidst the chaos on the bump, rookie right-hander Tanner Houck emerged as a glimmer of hope for Boston’s pitching future. The 24-year-old dazzled every time he toed the rubber, allowing just one earned run in 17 innings of work while striking out 21.

His success was rooted primarily in the usage of his slider, a pitch that could one day become every MLB hitter’s greatest nightmare.

Houck’s slider showed great potential.

When Houck was drafted by the Red Sox in the first round back in 2017, scouts graded his slider as a squarely average pitch. However, his performance at the major league level this year seems to suggest that it’s anything but.

Houck leaned on his slider heavily in the three appearances he made this year. He threw it 35.5% of the time, making it his second-most used pitch behind only his four-seamer (37%). That seems to have been the right move because, in 18 plate appearances, not one of his 94 sliders were put in play for a hit according to Baseball Savant.

And that .000 opponent batting average was no stroke of luck. 10 of those plate appearances ended in a strikeout, and only five ended with a ball in play. Opposing hitters had just a .065 expected batting average against the pitch.

His slider was so filthy that 47.2% of all swings against it failed to make contact, putting him on par with one of baseball’s best frisbee-throwers.

That player is San Diego Padres star Dinelson Lamet, whose slider was the most valuable pitch in all of baseball in terms of run value. Opposing batters managed a paltry .162 xwOBA against it, only marginally worse than the .182 mark they managed against Houck’s slider. Additionally, their .097 xBA against Lamet’s slider was actually better than it was against Houck’s.

Now, this is not to say that Houck already has the best slider in baseball. After all, he threw his slider just 94 times this season, a number nowhere close to the 553 thrown by Lamet. He still has plenty left to prove before he can claim to have baseball’s most devastating pitch.

However, using Lamet as a measuring stick proves that the potential is there, and it shows not only in his statistics but his mechanics as well.

At first glance, Houck’s delivery seems fairly orthodox. However, a little bit of video mirroring, courtesy of Rob Friedman, reveals that it bears a striking resemblance to the unique wind-up of seven-time All-Star and fellow Boston Red Sox hurler Chris Sale. Houck and Sale are almost identical in height, standing at 6-feet-5-inches and 6-feet-6-inches, respectively, and they both incorporate their length into their motion.

The resemblance is uncanny.

In fact, Houck’s slider doesn’t look too shabby in comparison to Sale’s. The young righty averaged 13.9 inches of break on his slider in 2020, just a fraction below the roughly 14 inches of break Sale has managed on his since he joined the Red Sox.

But once again, we must not get ahead of ourselves. It would be foolish to say that Houck is destined to become the right-handed version of one of baseball’s most feared strikeout artists. It’s simply unreasonable to expect that out of him based on a small 17-inning sample from a highly irregular season.

Considering how much trouble the Red Sox have had in grooming home-grown pitchers over the last decade, cautious optimism is the name of the game.

Ultimately, there’s nothing not to like about his slider’s profile. It showed all the hallmarks of being a lethal putaway pitch during his September stint in the majors, and if he can continue to hone it, he could end up making his opponents sweat every time they step in the batter’s box for years to come.