Villanueva, who has spent the entire year pitching in long relief, was promoted to the rotation following a pair of inconsistent outings by right-hander Jesse Chavez.
A starting role is nothing new for Villanueva, as the Dominican native has made 40 career starts, including 13 with the Blue Jays last season.
"I was always a starter and I like to be in control of things, so when I'm starting, I'm in control from the first pitch of the game," Villanueva said of his desire to start. "If you're going to ask me selfishly, of course, but I'm not a selfish person. If they want me to do whatever, I'll do it. I'm getting an opportunity to help the guys out in this role and I'll do the best I can."
This is the second consecutive year that Villanueva has been pressed into starting duties. Last season, he replaced an injured Jesse Litsch and proceeded to make 13 starts.
The first nine outings went extremely well, as he posted a 4-1 record with a 3.67 ERA. The final four didn't go nearly as smoothly, in part because of a lingering right forearm injury that eventually forced Villanueva onto the disabled list.
In those last four starts, Villanueva went 1-3 with a 9.31 ERA. He feels this year he is much more prepared to handle the rigors of taking the mound every fifth day for an extended outing.
"The season prior I prepared to throw 60 or 70 innings out of the 'pen," said Villanueva, who lost more than 30 pounds during the offseason. "Even my friends asked me, 'What if you start?' And [I] was like, 'Yeah, I got no chance.' But this year with what happened last year, I just didn't take any chances.
"I came in a little better shape this year and maintaining all year a little more vigorous workout routine, so that should help me physically at least. It won't come as a surprise to my body."
Manager John Farrell said that Villanueva should be able to throw approximately 75-85 pitches in his first start. Villanueva will be gradually stretched out over time, and Farrell added that he is now in the rotation to stay.
Toronto's starting rotation has been decimated by injuries in recent weeks. Right-handers Brandon Morrow, Kyle Drabek and Drew Hutchison are currently on the 15-day disabled list, while Henderson Alvarez was forced to depart Monday's outing with right elbow soreness.