Bedard underwent an MRI exam in Los Angeles on Thursday and the results were announced prior to Friday night's series opener against the D-backs.
"He can't throw for three days and then he'll be on a pitch count," manager Don Wakamatsu said. "The only thing they could find at all was slight bursitis, but you never know with those things and exactly what it is. That's the only thing they could come up with."
The Mariners put Bedard on the 15-day disabled list, retroactive to June 8, the day after his most recent start. He is eligible to be activated on Tuesday, but will remain on the DL for about another week. He is tentatively scheduled to return to the rotation when the Mariners open a three-game series against the Yankees on June 30 in New York.
The latest physical setback is not related to the injury Bedard had last season, which caused him to miss the second half of the season.
"We don't think what he's going through right now is related to last year," Wakamatsu said.
Bedard has been a consistent contributor to the rotation this season, compiling a 5-2 record and 2.47 ERA in 11 starts.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.