“We try to mix the four and the two, give them a different look,” Happ said. “Anybody that just sits there and throws fastballs, eventually you’re gonna get hurt. So we try to give them a different look and mix things up. But I definitely pitch off my fastball, trying to change eye levels a little bit. That’s important for me.”

By Fangraphs’ analysis, only three starters throw fastballs more often than Happ: the Mets’ Bartolo Colon, Happ’s Toronto teammate Aaron Sanchez and Milwaukee’s Jimmy Nelson. Happ throws fastballs 70.8 percent of the time, and that was before Thursday, when he used it for 78 of those 96 pitches.

It was not a flawless performance. Happ allowed solo homers to Gary Sanchez, Starlin Castro and Chase Headley in the 7-4 victory, and the runner he left on base in the eighth inning came around to score. His E.R.A. is 3.05, and the Blue Jays average more than six runs per game when he starts.

But Happ’s leap from a mid-rotation starter to something close to an ace, at 33, seems to be real. His work last summer with the Pirates’ pitching coach, Ray Searage — which built off Happ’s own adjustments in Seattle — helped him from pulling open too soon in his delivery. Finding and repeating the right arm angle — not too high, not too low — helped Happ believe he could rely heavily on fastballs and win.

“If you’re on the two-seamer, you’ll get beat by the four-seamer,” Blue Jays catcher Russell Martin said. “If you’re on the four-seamer, then you’re probably going to hit a ground ball with the two-seamer. And he just has a natural ability to elevate and throw it right in that spot where guys swing the bat. He hits the top of the zone — sometimes he goes just above the top of the zone — and he has enough life on it to just get it by guys.”

As it stands now, Happ should have a full week to prepare for his next start. The Blue Jays are using six starters, allowing them to reduce the workload on Aaron Sanchez, a young star they want to keep in the rotation. Marcus Stroman has also exceeded his previous career high for innings, and Marco Estrada has dealt with back trouble.

As an established, healthy veteran, Happ is not sure how much the plan benefits him.

“I don’t know if it’ll help me at all,” he said. “I guess we’ll just see how it plays out. I don’t anticipate it being a full two-month thing; I think something will eventually happen. But if it is, we’ll go with it.”