Still, when he walked back from the mound towards the dugout after retiring the side in the bottom of the first inning and saw C.C. Sabathia walking onto the field, even he had to admit the significance.
They first met when they were teenagers playing in the same summer league in the Bay Area. Sabathia called Willis the day the Indians drafted him, and Willis was with Sabathia at a Golden State Warriors game soon after Sabathia won the American League Cy Young Award last fall.
Even their families know each other.
"We've got the same financial advisor," Sabathia said, "so our moms are pretty close."
Yet through all the years, they had never had the chance to pitch in the same game against each other until Saturday. It was the first outing this spring for both of them, and it may well have served as a fitting backdrop for the season. Between the number of matchups between the Tigers and Indians each year and the prominence both pitchers have on their staffs, it would be shocking if it were their last meeting.
"We always laugh and joke about competing against each other," Willis said. "I know he's going to go out and play his hardest for his club, and he expects the same out of me."
The expectations for their respective teams make for what should be a summer-long playoff chase in their corner of the Midwest. It's a long way from where they grew up.
While Willis was born and raised in Oakland, Sabathia grew up in Vallejo, about 25 miles to the north. They were born about a year and a half apart, and their career paths have had some striking similarities.
Both emerged as standout players almost immediately upon arrival to the big leagues. Sabathia made the Indians rotation out of Spring Training in 2000 at age 20 and won 17 games, helping Cleveland get back to the playoffs on the tail end of their run of success that began in the mid-90s. Willis was a late May callup at age 21 and won 14 games for the Marlins, who became baseball's Cinderella story on their way to a World Series crown in 2003.
Both had to assume frontline roles on teams that began rebuilding soon after their rookie success. Both had to deal with contract issues -- Willis handling the questions about a long-term deal and trade rumors that followed him until Florida finally dealt him to Detroit last December, Sabathia now being peppered by the questions about his impending free agency next winter that has put his future in Cleveland in doubt.
"He loves the game and he loves being competitive," Willis said. "No amount of money will take that away. He's doing fine. He understands that he's a competitor and he's a guy that prides himself on going out there and battling. You can't put a price tag on that."
Both have a unique touch to their games. Sabathia's big frame and bigger uniform are almost impossible to mistake for another player when he takes the mound, just as Willis' high leg kick in his delivery is a signature.
Yet to understand their connection and their mutual admiration requires going back to their time growing up. They never faced each other, but they understood each other. They were two African-American kids starring in a game that has had too few stars to which they could relate, and they both made it through support from their mothers and through hard work. They're both involved nowadays with other big-leaguers in trying to get more African-American kids interested in the sport.
It's something they fall back on even now and admire in each other. When Sabathia won the Cy Young, Willis said, "I felt like we both won.
"I know what he's about. He's a guy that takes a lot of pride in going out there and taking the ball. He understands the importance of him going out there and representing African-Americans across the nation, so I was real happy for him. I'm real proud for him, and he's the same for me. It's fun seeing him like that."
For Sabathia, it was fun seeing Willis like he was in that strange sight on Saturday, pitching in a Tigers uniform. Sabathia has never had a chance to face the Marlins in his career, let alone Willis.
Though Willis faced the Indians last summer, Sabathia said that Saturday, "was my first time getting to see him pitch up close."
It certainly won't be his last. Since they'll have so many common opponents, Sabathia theorized that their conversations could include some scouting reports on other opponents. When Willis faces the Indians or Sabathia meets the Tigers again, however, even their friendship has its limits.
"I'm happy for him," Willis said. "He's a good friend. But I want my team to win. I'd expect him to want his team to win."
Interestingly, though, Willis doesn't expect the rivalry to be any more intense when they pitch against each other. Unlike Jeremy Bonderman, who loves to pitch against his good friend Rich Harden in Oakland, Willis isn't big into personal matchups.
"I tried that when I was younger," Willis said, "and it didn't go too well. When you do that, you overlook people, and people take it personally. ...
"We care for each other, but you can pretty much ask anybody around the league. I get a kick out of about anything. I play hard."
Said Sabathia: "When I'm on the field, I want to win. That's what I'm out there to do. I don't care who's out there. Off the field, we can be the best of friends. But when it's time to go, it's time to go."
Fortunately, they're teammates in the American League, where they don't have to bat. Asked who is the better hitter, Sabathia answered quickly.
"Me, of course," Sabathia said. "What kind of question is that?"
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.