The 2003 National League Rookie of the Year and two-time All Star has bounced around the league since the promising start to his career, but Willis will toe the rubber for the Reds and make his 190th career start Sunday.
"It's been a long road for him, and he's earned his way back here," Reds manager Dusty Baker said. "We didn't give it to him. We gave him an opportunity and he seized the opportunity, and that's the one thing that I can promise anybody -- the opportunity. It's up to them to seize the opportunity, so hopefully he can give us a show."
The Reds haven't formally promoted Willis from Triple-A Louisville, but he walked around the visiting clubhouse at Miller Park before Saturday's game. Willis watched film, and All-Star right fielder Jay Bruce said he spoke briefly with Willis.
"He's got the stuff, he's got the talent, he just has to figure out mentally what he has to do to be successful," Bruce said. "Hopefully, he can be a spark for our team."
Baker said he's seen many players sent down to the Minor Leagues who never return to the big stage, but he's hoping Willis can be one of the few who succeeds during his return. Willis posted a 71-63 record during his eight years in the Majors, which included five years spent with the Marlins, three years with the Tigers and one year with the D-Backs.
Willis went 5-2 with a 2.63 ERA with Louisville this season, and Baker said there's nothing physically wrong with the left-handed pitcher.
"There were a number of guys that fell from the graces of up above and returned with a renewed knowledge, wisdom and desire to never return back to the Minors," Baker said. "Sometimes you've got to take a step backward to take four or five steps forward, and we'd like to be the recipient of his forward movement."
Willis' first Major League start since June 29, 2010, will close out the first half of the season for the Reds. Willis is 3-2 all-time against the Brewers with a 2.65 ERA. Baker said he's not targeting any specific stats to measure Willis' return except for one thing.
"Just win," he said. "I don't care what the score is, just win."