"I wonder how bad it will be," the Seattle Mariners left-hander said.
Bedard had to leave Friday night's game against the Atlanta Braves after three scoreless innings because of spasms on the right side of his back.
"I've never had a back spasm before," Bedard said. "Now I sure know what they are. I had to be helped up the hallway [to the clubhouse]. I couldn't walk."
"We really won't know [anything more] until he wakes up," interim manager Jim Riggleman said. "He was very uncomfortable."
Bedard said he felt much better after the game, but he didn't know how stiff he would be after a night's sleep.
The Mariners are already without reliever Brandon Morrow, who didn't make the trip to Atlanta because of back spasms.
Bedard allowed two hits, both singles. He struck out one and walked none, throwing 36 pitches before being replaced by Roy Corcoran to start the fourth inning.
Bedard pitched an inning after hitting a single in the top of the third and being forced out on a double play. He doesn't think that the back spasms are related.
The former Baltimore Orioles standout said that he felt his back stiffen on a 3-2 pitch to Ruben Gotay, who singled. Gregor Blanco hit into a double play to end the third inning.
"When he walked off, the closer he got to the dugout, the more pain you could tell he was in," Riggleman said.
Bedard, acquired in a big offseason trade, is 4-4 with a 3.97 ERA in 13 starts. He was on the disabled list in April because of hip inflammation.
Guy Curtright is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.