That's the question the D-backs' brass is asking itself after placing starter Joe Saunders on the 15-day disabled list on Saturday with inflammation in his shoulder.
Saunders' turn in the rotation will come around again on Thursday. It's possible that with Monday's off-day, the D-backs could bring Ian Kennedy back on regular rest to start on Thursday, but that would mean Saunders' spot would come up on Saturday.
"That's something we're talking about," D-backs manager Kirk Gibson said. "It's to be determined. We've got several options. We'll just get through and see what the next couple of days bring us and continue to evaluate what we want to do."
The options include calling up Bauer, the No. 3 overall pick in last year's Draft, who has pitched well at Triple-A Reno. Patrick Corbin, who made five starts for the D-backs earlier this year and is also at Reno, could also be chosen.
The D-backs could also decide to use Josh Collmenter, who made the start on Friday when Saunders had to be scratched at the last minute. Collmenter has pitched well out of the bullpen after struggling in the rotation in April.
"That's one of the things we struggle with," Gibson said. "If we start him, then we lose that versatility out of the bullpen. How do we cover that up?"
Gibson was asked specifically about Bauer, whom the organization has asked to improve his ability to hold runners on base and be more economical with his pitches.
"I think he's a candidate probably as well as anybody," Gibson said. "Is he ready? How do you know? There's certain things he does great. We all know he has great stuff. His last two starts, he's had 100 pitches in five innings.
"If I was Trevor, I would argue I would get better with better competition and I think that's how he probably thinks. I don't know that we know that answer. We'll consider all options."
Bauer is 4-0 with a 2.79 ERA in seven starts for Reno, while Corbin is 3-2 with a 3.86 ERA in six starts.