Villanueva, whose last start was May 14, has posted a 2.04 ERA in 16 games as a reliever. He didn't feel he needed much time to prepare.
"The last two years, I've basically thrown without any buildup," he said. "I remember in New York, my first game in May, I went 75 [pitches], and last year, I went 95 in my first start in July. It's not the way you want to go and they're taking care of me here."
The Cubs need a starter to fill in for Scott Feldman, traded on Tuesday to the Orioles.
"We lost 'Feldy,' loved him, great teammate," Villanueva said. "I'm happy to see him go to a contender, but obviously, I'm sad for selfish reasons because he was a really good teammate. We've got the rumors swirling around [Matt] Garza. You've got to be prepared for it. The team has to do what's best for the future, obviously."
Although Villanueva has done everything but pick up a save this season, he does like starting the best.
"I've always been a starter, ever since I was a kid," Villanueva said. "I like having the control from pitch one. I'm sure all of our bench players would like to be starting."
But he'll never complain about his role.
"I want to be a guy who isn't trouble," Villanueva said.
He was 1-3 in eight starts with a 3.93 ERA.
"If there's an opportunity for me to help the team out, I feel with me starting, we have a good chance to win," he said. "From the heart, that's how I feel. I feel like I'm prepared, I feel like I'm matured. If I get a couple more starts, I'll try to do my best so I can get a full-time gig next year."