Enrique Gonzalez will take Villarreal's spot in the bullpen. The 28-year-old began the season in Detroit before being sent down after a rocky start. He's pitched pretty well in Toledo, going 1-1 with six saves and a 4.22 ERA in 10 appearances.
Villarreal has struggled this month after a solid April. He allowed two runs in a loss to Pittsburgh on Friday.
The 35-year-old Guillen hasn't played since having microfracture surgery on his left knee last September.