"The stuff wasn't good," Hughes said. "It's one of those things where if you don't have good stuff and leave the ball over the plate, things like that are going to happen."
Gibson, who is on the DL retroactive to April 23 with a right shoulder strain, was slated to start against the Rays after faring well in two rehab outings with Class A Advanced Fort Myers. But he said his back started to bother him on Monday, and didn't get any better, so the Twins decided to be cautious and push back his start.
"It's disappointing news," Molitor said. "He did everything we asked to get that shoulder back in shape. As we all know, we had him slated to pitch tonight. I think after his last bullpen he was fine and got some work in, but felt some discomfort in his lower back and pain going down into his leg. So we had it checked it out, but nothing major. He feels it more when he's sitting for a long period of time."
The Twins are debating whether Gibson will make one more rehab assignment with Triple-A Rochester before being activated from the DL. But the good news is he threw a 40-pitch bullpen session to test out his back on Thursday, and he said it went well.
"I was hoping to come in today and see how it felt, but I didn't want to put the team in a bind," Gibson said. "Especially if I went out there and lasted two or three innings. I had to do what's best for the team. But I threw a bullpen today and it felt fine."
Gibson, who has dealt with back issues in each of the last two seasons, said this injury is different, but not as serious as the back spasms he's had in the past. Gibson said his first inclination was to try to pitch through it, but it didn't make sense to risk further injury, especially coming off the shoulder issue.
"This one creeps more into the sciatica more and has a little more nerve pain," Gibson said. "It's not nearly as bad, but it's still muscular. I don't want to be out there compensating coming off the shoulder thing. That's a bad combination."
Rhett Bollinger has covered the Twins for MLB.com since 2011. Read his blog, Bollinger Beat, follow him on Twitter @RhettBollinger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.