TORONTO -- When the Blue Jays broke camp at the end of March, Trent Thornton was a rookie with a loose grip on a rotation spot. By the time the season ended, Thornton led the club in starts and innings pitched while representing the one surprise constant in the rotation.

After beating out Thomas Pannone and Sam Gaviglio for that rotation spot out of Spring Training, it seemed likely that the eventual return of either Clay Buchholz or Ryan Borucki would bump Thornton back to Triple-A. That moment never came, though, and the 26-year-old right-hander went on to post a 4.84 ERA over 154 1/3 innings. As the Blue Jays battled injuries alongside the trades of both Aaron Sanchez and Marcus Stroman, Thornton’s starts were one of the few forms of consistency on an ever-changing roster.

Acquired last offseason from the Astros for Aledmys Díaz, Thornton has now positioned himself well to lock down a rotation spot in 2020 and beyond.

What went right?
Thornton’s season offers a valuable glimpse at what continued development looks like at the Major League level. There were highs and lows through the early half of the season as Thornton adjusted to the big leagues -- and life in the American League East -- but he finished strong.

In September, Thornton posted a 2.19 ERA over his final five games (two starts), and his pitches remained sharp despite the physical toll of his first full MLB season. Thornton was open throughout the season about his need to do a better job controlling his mental game, and he made strides in that area with the help of the Blue Jays’ staff and their rostered veterans, like Buchholz.

“I think he’s going to get better and better,” Blue Jays manager Charlie Montoyo said. “The more he pitches, the more he knows the league, the more strikes he throws. Whenever his command gets really good, he’s going to be a good pitcher for a long time, I believe.”

What went wrong?
Inconsistency followed Thornton for much of the season, which is to be expected from a rookie whose delivery has so many moving parts.

Thornton was evidently searching for the optimal pitch mix and his consistent control, which he would find for stretches of two or three starts before hitting some turbulence again. His fastball, which averaged 92.9 mph according to Statcast, and hammering curveball both have the potential to be above-average pitches in the big leagues, but the development of his secondary pitches will be key.

Enter Buchholz, who Thornton praised often this season for his mentorship. Buchholz and Thornton tinkered with Thornton's changeup and curveball grips, which brought some encouraging results late in the season. A full winter to make those grips feel more natural will help, both in terms of their consistency and Thornton’s confidence in throwing them.

“I’ll be able to work on it a little bit more,” Thornton said, “but ultimately, you just have to trust the pitch you’re throwing and have full conviction in it, as well.”

Best moment?
Thornton got his first crack at his old team, the Astros, on June 16 in Houston and turned in one of his best performances of the season.

Over 6 2/3 shutout innings, Thornton danced around six hits and three walks while striking out seven, including Yordan Alvarez twice. There were a handful of Thornton’s pitching lines that look similar to this Astros performance, but his performance against a lineup of that quality and ability to balance his emotions on the mound make this one stand above the rest.

2020 outlook?
If the season started today, Thornton would be in the starting rotation. The same will probably be true when the season actually starts, but plenty can happen between now and then, as the Blue Jays are expected to be aggressive in their pursuit of multiple starting pitchers.

“Nothing is etched in stone,” Toronto general manager Ross Atkins said in early October. “I think Trent Thornton has probably put the best foot forward, but his offseason will be very important. A lot of guys could make huge strides.”

If Thornton can take one of those strides himself and drag his 4.84 ERA down by half a run, he’ll have value over another full, healthy season. Until the Blue Jays’ offseason plan becomes clearer, Thornton has the clear inside lane on a permanent rotation spot in '20.