D-backs manager Kirk Gibson said the team was considering options for Monday, which is Collmenter's day to pitch.
"We may move him to the bullpen," Gibson said. "We're considering it. He may not start Monday. We're considering other options. We'll probably make a decision by [Saturday]."
Collmenter was outstanding for the D-backs in 2011, going 10-10 with a 3.38 ERA in 31 games (24 starts) and won a big game for the club in the National League Division Series against the Brewers.
This year, though, it's been a different story.
Collmenter struggled during Spring Training and then into the regular season. In his first four starts, he went 0-2 with a 9.82 ERA.
If the team chooses to dip into the Minor Leagues for a replacement for Collmenter, Double-A left-hander Patrick Corbin would seem to be the leading candidate given that his last start was the same day as Collmenter's -- Tuesday.
Fellow Mobile left-hander Tyler Skaggs would also be a candidate. His last start was Wednesday, which would mean he would be pitching on regular rest.
Corbin is 2-0 with a 1.67 ERA in his first four starts, while Skaggs is 0-2 with a 4.24 ERA in his first four.