Trent Thornton: The 2019 Blue Jays’ Sole Starter

After the 2018 season, the Toronto Blue Jays began stockpiling starting pitchers. It was a necessary stage in their rebuild. Forget about quality innings, the roster was in desperate need of arms any way possible. Even with this foresight, Toronto ended up running out a knuckleballer (Ryan Feierabend), a two-time Tommy Johner (Daniel Hudson) and of course, a whole lot of openers. But it was their most reliable hurler who has generated all the intrigue.

Amid their 2019 pitching preparations, the Blue Jays acquired Trent Thornton. The starter had yet to make his major league debut, pitching four generally successful seasons in the Astros organization. The young righty featured strong strikeout rates in the bookend seasons of his tenure as an Astro, again, offering productive, yet unexciting innings.

From there, breaking camp with Toronto in 2019, he could have easily dropped off, displaying some turbulence during his stride to the major leagues, but he didn’t. Instead, he was by far Toronto’s most dependable starter. The next closest player to Thornton’s 29 starts who played the whole season with Toronto was Wilmer Font, who’s 14 starts included a myriad of appearances as an opener. Thornton wasn’t just Toronto’s most reliable starter, he was their only full-time starter. Nothing to brag about in any other organization, but with Toronto, his value was magnified. And that doesn’t presuppose his performance – which left reasons for optimism.

Nobody is going to grant a Cy Young award to Trent, but after a full season of work, he’s all but guaranteed himself a spot in the 2020 rotation. Again, none of a 4.84 ERA, 94 ERA+ or 1.406 WHIP will stand out. But digging a little deeper illuminates his promise. Firstly, his strikeout rate was strong. 8.7 K/9 or 22% is nothing to sniff at. It’s a high he’s attained in the minor leagues and his ability to sustain it at the major leagues is exciting.

One of Thornton’s most interesting offerings, powering that strikeout rate, is his slider. In 2019 it led all of Major League Baseball with a whopping 52.3 inches of vertical movement, 21% more than average (fourth). It also sits five miles per hour slower than the average slider, making it especially foreign to hitters.

Cred. Tom Szczerbowski/Getty Images

Despite throwing it just 8.9% of the time, Trent does feature a split-finger fastball, something he’s used most often against lefties. Even after throwing it just 246 times, it’s been effective. Disregarding that sample size, it’s his best pitch. He dominated hitters with it holding them to a .120 batting average, .160 slugging percentage and .152 weighted on-base average. Now, all those numbers were below their expected equivalents, however, even inflating those rates won’t alter the fact that the pitch was successful. 

His cutter has acted as a strong stabilizer in his mix, offering a place to go when he doesn’t want to expend his secondary pitches or needs an alternative to the high-speed fastball. While it comes well regarded, ranking 22nd in horizontal movement, the cutter hasn’t yielded the same success Trent’s other pitches have. He’s struggled to record outs with it, posting a .299 BA, .474 SLG and .366 WOBA. Throwing it third most often, 15.9% of the time, improving the results of his cutter is certainly a prerequisite for continued success.

Finally, his four-seam fastball, consuming 43.6% of his pitches, comes in at an average velocity of 92.9 miles per hour. It’s effective, as all primary pitches must be. However, it could be a lot better. Results-wise, the fastball has been average or worse (.265 BA, .510 SLG, .369 xWOBA). Things get interesting when the pitch’s attributes are analyzed. Despite subpar horizontal movement, his vertical movement sits a little above average. Furthermore, ranking 23rd, it’s got good spin. However, of the pitchers who boast superior spin rates, well more than half have weaker velocities. This is where we can extract some insight into Trent’s next steps.

Thornton’s spin efficiency is poor. Again, both his spin and velocity rank in the top 40, middle class. However, when you consider what his spin is doing for the pitch, Thornton is not being very productive. His 73.2% spin efficiency ranked 581st of 690. You can see above, except for that elite slider, none of Thronton’s pitches effectively utilize spin to generate movement, the issue plagues his entire pitch selection.

There’s another step Thronton could take to turn the corner and develop into an elite starter. In Trent’s case, there’s less evidence that poor pitch tunnelling has resulted in poor performances, but it’s difficult to imagine batters aren’t picking up on his spots. Below are release points from two starts, the top from a July start, where he surrendered 11 hits, 7 earned runs through two and two-thirds innings of work against Boston. The bottom one is from May, where he shutout the Rangers over seven innings, allowing a lone hit. 

In neither start did he tunnel his pitches very well – at all – even pitches of like type were poorly organized. Thornton does feature a somewhat wild leg kick. That’s not a knock, however, if the added motion in his lower half  renders him unable to make his release point consistent he may have to make a change. But he’s been successful without even a consistent release point, nevermind pitch tunnelling. 

So is his lack of tunnelling and inconsistent release point sustainable? It’s impossible to say. Only time will tell. Thornton does suffer from the third time through the order tax, quite significantly. This may be an indication that hitters do pickup on his scattered, unique release points. Or it could just be a highlighted, emphasized case of what all pitchers suffer from.


Ultimately, the Blue Jays have an interesting future value piece in Trent Thornton. Some careful player development with special attention to modern analytics could turn an Astros farmhand into a frontline starter for a team that is right around the corner from contention. A period of contention Thronton will no doubt contribute to.

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