And he certainly didn't expect to be bringing Miguel Cabrera with him.
"As soon as I heard it, I didn't really believe it," Willis said in a conference call with reporters on Wednesday evening.
Willis had just landed in Mexico on a vacation with some friends and fellow clients of agent Matt Sosnick when he learned he'll be spending April in a far more northern climate than South Florida. But after pitching in the Midwest League as a teenager, he said he's prepared for it. In many ways, he's been preparing himself for this type of home for a while.
"In trade talks, you never really know," he said. "All I really heard was speculation. I was definitely caught off guard."
So, of course, was the rest of baseball, not to mention the rest of the Tigers roster.
"Wow," closer Todd Jones wrote in an email Wednesday. "I can't believe this happened to us. Mr. Ilitch knows we're close, so he did this to put us over the top. I'm so thankful as an older player to have the opportunity to be on a team like this."
Kenny Rogers was equally stunned.
"To get a couple players of that caliber," Rogers wrote in an email, "to go along with the team we already have, is astounding!"
Willis brings a combination of experience and youth. A month shy of his 26th birthday, he has five big league seasons and more than a thousand Major League innings to his credit. He has averaged 215 innings a year in his four full big league seasons. Yet he hasn't had a chance to be on a playoff team since he was a rookie on the 2003 world champion Marlins.
Now that he's back with Pudge in Detroit, that seems about to change.
"Aw man, they're very good, very talented," Willis said. "It's a team that loves to hit as well as defend. They have some power arms in the bullpen, as well as starting [pitchers]. They're a complete ballclub. I actually know a lot about them."
He knows plenty about the players, starting with Rodriguez. It was in Florida where Pudge gained a reputation for working well with young pitchers, and Willis was the prime example. As Willis recalled, Rodriguez knew quickly what kind of stuff he had one day and whether it was different on another.
As for Rodriguez's personality, Willis fed off of it.
"You've seen he's a very fiery guy, a very emotional guy," Willis. "He's a very positive guy and a guy who expects a lot out of himself. I'm the same way."
He expects more out of himself this year than his most recent numbers would suggest. His 5.17 ERA last season was the highest in his career by more than a run, and his 15 losses marked a career high. Yet he felt like he ended on an encouraging note. In his last three starts, he scattered six runs over 16 2/3 innings with 15 strikeouts. To him, it was a home stretch of health after a season battling injuries.
"Towards the end, I started to feel better and started to get my command back," he said. "Hopefully I can continue to throw the ball like I did my last couple starts."
He would love to do so in a city where he could be a role model as an African-American starting pitcher.
"I take a great deal of pride in that. Always have," he said. "I definitely wear it on my shoulder and on my heart, because I know the opportunities that guys like Dave Stewart have made for me. I want to go out there and hopefully they see the sincerity in my game and appreciate it."
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.