"I didn't really feel too good [Wednesday]," Corbin said. "I don't know why; just one of those days. Just mechanics and everything, I kind of felt like I was rushing everything, just really couldn't locate. I was throwing a lot of off-speed pitches and fell behind a lot of the hitters.
"Just one of those days where I didn't feel that good. I don't know if my arm wasn't as loose, but I just felt like I was rushing my mechanics a lot."
The big blow of the inning was a grand slam by Kansas City's Alex Gordon, but what most concerned manager Kirk Gibson was Corbin not being able to make adjustments during the inning.
"When it starts like that, you have to fix it," Gibson said. "Inevitably if you don't fix it in a game, that's what's going to happen for him."
With the longer Spring Training this year due to the World Baseball Classic, there is still plenty of time for one of the three pitchers to separate themselves .
"I'm not in any hurry for that," Gibson said regarding choosing a No. 5 starter. "We've got a long way to go. We've got 25 games left? There's a long, long way to go. We'll continue to take it in and watch it."
Steve Gilbert is a reporter for MLB.com. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.