Toronto's right-hander has yet to appear in a game because of a bizarre hand injury he suffered at the beginning of camp. Late last month, Villanueva experienced a cold sensation in his hand, which the club believed was related to a circulation problem.
Villanueva has since returned to the mound and pitched during batting practice on Sunday morning without any ill effects.
"No issues today -- a day later -- and he's set for a simulated game on Wednesday," Blue Jays manager John Farrell told reporters prior to Monday's game against the Tigers. "So [he's] making very positive strides to hopefully get back into a game some time on the weekend."
The 27-year-old Villanueva is considered a strong favorite to win one of the final two spots in Toronto's bullpen. He is facing competition from Luis Perez, Evan Crawford and Rick VandenHurk.
Villanueva went 6-4 with a 4.04 ERA in 20 appearances out of the bullpen and 13 starts in 2011. The six-year veteran is 26-28 with a 4.28 ERA in his career.