Manager Charlie Montoyo said Thornton has earned a spot in the Blue Jays' Opening Day rotation, Shi Davidi of Sportsnet.ca reports.
Thornton will temporarily open the season in the rotation thanks to injuries to Ryan Borucki (elbow) and Clay Buchholz (elbow). The 25-year-old right-hander held his own this spring, compiling a 4.80 ERA, 1.20 WHIP and 16:5 K:BB through 15 innings. With Borucki and Buchholz both getting healthier, however, Thornton may only have a few starts to prove he deserves to stick in the majors. His first start will come against the Tigers on Sunday.