Villanueva took the loss in the Cubs' first two games Monday and Wednesday, pitching in relief. His start on Sunday was in question because of the workload, and manager Rick Renteria said he would talk with Bosio to go over their options.
As far as Villanueva is concerned, he's starting in the series finale against the Phillies.
"I'm in on Sunday," Villanueva said. "Unless they tell me otherwise, I'm in."
Villanueva won the fifth spot in the rotation, and he was expected to stay there until Jake Arrieta is activated from the disabled list. Arrieta, slowed this spring by tightness in his right shoulder, was to make his first Minor League rehab start on Saturday for Double-A Tennessee in Pensacola, Fla.
Losing the first two games, both extra-inning losses, was tough for Villanueva, but also part of the job as swingman.
"For me, it goes back to doing whatever it takes in whatever situation," Villanueva said. "It would've been nice if it came out the other way. I feel pretty good. It happened quick. The full inning [Wednesday], I felt pretty good that inning.
"In those situations, you can't really make a mistake, and I made two mistakes, I'd say," he said. "I made the mistake to [Starling] Marte with a high changeup, and a high changeup to [Neil] Walker. I worked on that in the bullpen today."