"I would say the answer to that, as we speak, is 100 percent no," Leyland said to questions of whether Willis could replace Robertson.
The Tigers have a program for Willis, who was optioned to Class A Lakeland in June to work on his delivery and iron out his control problems. While his effort has progressed to Triple-A Toledo, the last thing the Tigers want to do is rush him back.
"I think the worst thing to do," Leyland said, "would be to panic and try to go against everything we've tried to do and replace Nate with Dontrelle. That would be the easy thing to do, but I think it would be the wrong thing to do right now, and so does [Tigers president and general manager] Dave [Dombrowski]."
The Tigers are trying to figure out whether it would be best for Willis to be with the big league team at all in September, once the Mud Hens' season ends on Sept. 1 and Major League rosters expand. Leyland said he and Dombrowski discussed the matter on Thursday night, and at this point, there is no clear answer.
"Would it be nice if Dontrelle was able to pitch for us in September? Yes," Leyland said. "Is that going to happen? I can't answer that."
Willis had mixed results in his second start for the Mud Hens against Norfolk on Wednesday. He allowed five runs, three earned, on eight hits over five innings with five walks and four strikeouts. Fifty-five of his 98 pitches went for strikes.
Leyland said the report he received on the game called Willis' delivery "real deliberate" and "methodical" in the early innings, before settling down later.
"I think they worked hard to slow him down a little bit," Leyland said. "According to the report I heard, he got a little too slow. And then after a couple innings, when he got into more of a rhythm, he was better. But his performance was not a good performance."
That backs up a story that appeared Thursday in the Virginian-Pilot of Norfolk, which also called Willis' delivery "deliberate," and went as far as to say: "He seems to be trying to lull [hitters] to sleep."
However, the story also mentions that the movements of Willis' delivery are more subdued than before, including his trademark high leg kick. Those were some of the mechanical changes sacrificed to regain some command, and adjust for the 26-year-old Willis' changing body frame as he matures.
"If you're young, you still have time to make some changes and come back," Mud Hens manager Larry Parrish told the paper. "But it's a lot harder to teach an old dog new tricks."
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.