The Toronto Blue Jays will begin the 2019 season with Trent Thornton in their rotation, which is a potentially interesting decision
On Tuesday afternoon, Blue Jays manager Charlie Montoyo announced that Trent Thornton would be taking Ryan Borucki’s spot in the rotation until Borucki was back to full health. The expectation is that Borucki needs to skip two starts for his recovery. While guys like Sean Reid-Foley and Thomas Pannone are more familiar to Jays fans and spent some time last season starting in the majors, going with Thornton makes a lot of sense and I’m extremely eager to see him in action.
Extensive Triple-A Experience
While Reid-Foley and Pannone both have more MLB experience than Thornton, Thornton has pitched nearly twice as many Triple-A innings (239.1) as the two pitchers combined (122). As I noted in my Top 61 prospects list, Thornton “was quietly effective [at the Triple-A level in 2018], producing a 4.01 FIP (65th percentile). He ran good strikeout (23.6%, 84th percentile) and walk rates (6%, 81st percentile), but gave up homers a little more often than average (0.94 HR/9, 46th percentile).”
Some important context is necessary for his somewhat-high home run rate. The Astros’ Triple-A affiliate is the Fresno Grizzlies, who play in the Pacific Conference of the Pacific Coast League. Across the Triple-A level, there are five divisions/conferences: three divisions in the International League (North, South and West) and two conferences in the PCL (American and Pacific). In 2018, the home run rates of the three IL divisions and the American Conference of the PCL fell in a tight range of 1.58 to 1.65 HR/9.
In contrast, the home run rate of the Pacific Conference of the PCL was 2.11 HR/9. As a result, when we compare Thornton’s home run rate against only PCL Pacific Conference pitchers (min. 80 IP), he ranks much more respectably (68th percentile). Moreover, among this group of comparables, Thornton’s FIP (86th percentile), strikeout rate (89th percentile) and walk rate (89th percentile) only stand out further.
Impressive Spin Rates
In their list of top Blue Jays prospects, FanGraphs’ Eric Longenhagen and Kiley McDaniel ranked Thornton tenth. They were most impressed by the extremely high spin rate he achieves on both his fastball and his curveball. At the moment, with 20 team prospect lists completed, Thornton is tied for 14th in fastball spin rate (2500 RPM) and ranks first in curveball spin rate (3100 RPM).
Generating a high spin rate on one pitch is great. Accomplishing this with two pitches is rare and impressive—Thornton’s spin rate average between his fastball and curveball (2800 RPM) is tied for first among those who have been evaluated by Longenhagen and McDaniel. He’s tied with Dustin May and just ahead of Forrest Whitley, two of the top pitching prospects in the minors.
As I mentioned in my post on FanGraphs’ Blue Jays list, “a high spin rate is useful for both pitches, though in different ways. A high-spin fastball (which has lots of backspin) remains up for longer, tricking batters who expected gravity to bring it down onto their swing plane. On the other hand, a high-spin curveball (which has lots of topspin) has more downward movement than expected, leading to lots of whiffs and grounders.”
In addition to his effectiveness at the Triple-A level (both in terms of quantity and quality) and his high spin rates, Thornton’s case for replacing Borucki is bolstered by his solid spring. He struck out plenty (25.8% strikeout rate) and walked batters at a pretty standard rate (8.1% walk rate). Importantly, he also avoided the long ball quite well—he ran a solid 0.60 HR/9 and didn’t give up a homer until his final game, against Gleyber Torres no less. Beyond the homer, he gave up three doubles, allowing a very strong .107 ISO.
Thornton’s 4.80 ERA might raise some eyebrows, but that was driven mainly by a low strand rate (60% LOB% vs. a normal level of 72% or so), which is very volatile in small samples like this. He gave up hits in clusters, resulting in more earned runs than expected given his underlying performance. For what it’s worth, with a more typical strand rate (72%), Thornton would have run an ERA around 3.60. That mark jibes a lot better with his strong fundamentals.
While Thornton may only wind up getting two starts in his MLB debut, they are well-deserved. He has performed well over many appearances at the highest level of the minors, as well as over a handful of appearances in MLB spring training. Moreover, his stuff seems quite dangerous. Even if he heads down to Buffalo after a couple of weeks in the majors, I think it’s likely his MLB experience will continue to grow throughout the 2019 season.
*Featured Image Courtesy Of DaveMe Images. Prints Available For Purchase.
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I’m an economics professor in the GTA whose lifelong love for the Jays was reignited by that magical August of 2015 and the amazing moments since.