Thornton showing worrying trends when Blue Jays need him badly

TORONTO — Five starts into his MLB career, it’s fair to say the Blue Jays don’t know what they have in Trent Thornton.

It is becoming clear, however, what they need him to be. With Matt Shoemaker going down to a torn ACL on Sunday, Aaron Sanchez’s finger worries reignited and Ryan Borucki’s return far from imminent, Thornton’s rotation spot is locked in for the moment.

Prior to Tuesday’s game, manager Charlie Montoyo said that he was looking at a running out four-man rotation until early May due to some off days, and Thornton is part of that four. Asking a guy with no MLB experience to help solidify a rotation that’s falling apart around him is a big ask, but the returns have not been great of late.

Following a 7-6 loss to the San Francisco Giants in Kevin Pillar’s return, Thornton has now allowed 14 earned runs in 12.2 innings of work in his last three outings with four home runs allowed.

Tuesday was supposed to be the perfect game for Thornton to get on track. The Giants entered action with a pitiful batting line of .209/.270/.332 and league-worst 60 wRC+. Even though their lineup has names like Buster Posey and Evan Longoria, it’s awfully short on guys who should scare you in 2019.

That’s why it was undoubtedly disconcerting for the Blue Jays to see Thornton struggle to get through five innings with four earned runs allowed.

“I felt pretty good tonight,” the rookie said, summing up his outing. “In the second inning I left a couple pitches over the plate. They’re big-league hitters, they’re going to do damage on stuff like that.”

There were certainly positives, as usual the right-hander broke off a couple of impressive breaking balls and his strikeout to walk ratio of 5:0 was significantly better than his last two outings - but there were undoubtedly more negatives.

Put simply, the Giants hit Thornton hard. His average exit velocity against was 92.2 mph. To put that in context, the league average is 87.4 mph and the Giants are not known as a collection of Statcast darlings.

Unfortunately for Thornton that performance is in line what we’ve seen from him so far. He entered the game with an average exit velocity against of 92.3 mph and a barrel rate against of 15.7 percent (way above the league average of 6.7 percent). Thornton has been relatively good at controlling the strike zone - as his K/BB ratio of 26:7 attests - but the contact he’s allowed has been extremely dangerous.

It’s hard to know exactly where his most recent problems lie. Whenever there’s a big disparity between K/BB numbers and overall results it’s a good indicator that command rather than control has been an issue. That’s certainly part of the problem for Thornton.

There’s also the matter of his fastball. Thornton averaged 93.7 mph on it in his MLB debut on March 31st. It was more than a tick down at 92.6 on Tuesday. That’s not awful by any means, but it makes a difference.

For instance, the heater he threw on Joe Panik’s home run - the second baseman’s first in 240 at-bats - came it at 90.7 mph. That’s awfully low for Thornton.

Thornton’s slightly diminished velocity certainly appears to have affected his pitch mix:

“I want him to be more aggressive with the fastball,” manager Charlie Montoyo said. “He was a little bit more today, but not as much as we’d like him to be.”

Throwing more fastballs isn’t necessarily better, in fact the trend around baseball today is to emphasize breaking balls and give opponents fewer heaters in the strike zone. That said, Thornton may have reached a point where the threat of his fastball isn’t at the front of opposing hitters’ minds and they are sitting on the curve or slider.

“I think I need to start throwing a few more fastballs and establish my command with that,” he said. “That’ll make all my other pitches better.”

It will be interesting to see if Thornton, and his batterymate - presumably Luke Maile - take that thought to heart in his next start. It seems like an adjustment of some kind is needed.

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