The team designated the big left-hander for assignment Sunday and recalled young left-handed reliever Jordan Norberto from Triple-A Reno. In his brief time with Arizona, Willis had the same control problems that plagued him in Detroit.
The Diamondbacks acquired Willis from the Tigers on June 1 for right-hander Billy Buckner, with Detroit picking up most of the pitcher's $12 million salary. In six games with Arizona, five as a starter, Willis was 1-1 with a 6.85 ERA. He struck out 13 and walked 27 in 22 1/3 innings.
Recently moved to the bullpen, his only appearance as a reliever was Saturday night, when Willis gave up three runs on three hits in one inning of Arizona's 14-1 loss to the Los Angeles Dodgers.
"He was a good soldier here, worked real hard, it just didn't work out," interim general manager Jerry DiPoto said.
Willis had welcomed the trade as "a fresh start." A little over a month later, he was gone. The team designated him for assignment three days after firing general manager Josh Byrnes and manager A.J. Hinch.
"We gave him this opportunity in an effort to try to resurrect him, to give him opportunity, and just catch lightning in a bottle," DiPoto said. "After just talking to him, it didn't particularly work this time around. Dontrelle's a wonderful human being. He works particularly hard, brings a lot of energy to a club and for that reason it was a little bit of a difficult decision."
DiPoto, a former major league reliever, wasn't going to hazard a guess as to what is wrong with Willis' delivery.
"I've seen Dontrelle pitch since he was a rookie in the league, like a lot of us have," DiPoto said. "He's always had a very unique delivery, so it's almost impossible to cite what he would be doing in his delivery that would cause the control issues. Whether it's mechanical, I can't tell you. Only he can sort that out."
Willis lost his starting job to Barry Enright, a 24-year-old right-hander who was called up from Double-A Mobile and held St. Louis to a run in five innings in Arizona's 4-2 victory over the Cardinals on Wednesday.
Norberto, 23, made Arizona's opening day roster but gave up three runs in three innings pitched over six games and was sent down to Reno on April 21.
With the Aces, he was 3-0 with four saves and a 3.07 ERA. Norberto struck out 38 and walked 19 in 29 1/3 innings with Reno.
The Diamondbacks had no lefty in the bullpen from the time Norberto was sent down until Willis went there a few days ago.
"We've got one now," interim manager Kirk Gibson said. "He's young. It's not like we could use him like a veteran guy. We'll have to try and put him in good situations, yet he may find himself in one that's not so favorable. He's confident. I know he's worked hard. When he went down we had him worked on some things. He's done what he's asked and it's made him better."