Initially, the team was planning on giving Chad Gaudin the final start. But when Tuesday's game dragged into the 11th inning, Gaudin entered in relief. The right-hander had a perfect inning, and he was credited with the win.
Koehler, a September callup, has made seven relief appearances, and he's not been involved in a decision. He has a 5.40 ERA in 8 1/3 innings, with 10 strikeouts.
During the Marlins' three-hour, 30-minute game, Mark Buehrle volunteered to take the ball on Wednesday. The left-hander was initially scheduled to pitch in the game, but he was shut down after reaching the 200-inning milestone. The lefty is 13-13 with 202 1/3 innings.
But because Buehrle didn't do any between-start throwing, manager Ozzie Guillen is refusing to let the veteran pitch.
"Koehler will pitch," Guillen said. "Buehrle told me he was ready to go, if he was needed. But he didn't go through his routine. I'm not going to put somebody in a spot to get hurt. If he was doing his routine from start to start, it would be different.
"But he didn't do anything for four days. I'm not going to risk any injury."
Carlos Zambrano, who is dealing with a sore knee, is also unavailable for Wednesday.