The MRI exam Bedard had last Friday disclosed some fraying in his labrum that wasn't detected during a similar exam taken several weeks ago.
Yocum, one of the highest-regarded orthopedic surgeons around, is expected to make a recommendation regarding surgery and it would be up to Bedard to make the final decision.
"I am not a doctor," Wakamatsu said, "but the preliminary thought is that it would not be a very dramatic surgery if he needs it."
There are about seven weeks remaining in the regular season, so the Mariners are faced with the reality that Bedard might have thrown his final Seattle pitch this season and possibly forever. He becomes eligible for free agency at the end of the World Series.
"I really don't know," Wakamatsu said when asked if he expected Bedard to return this season. "We'll know more tomorrow."
Bedard had a cyst removed from the same shoulder last year and seemed to have a successful recovery, reporting to Spring Training ready to join the rotation on a full-time basis.
But, just like last season, he reached the 15-start mark this season and has not pitched since.
His most recent appearance came on July 25 against the Indians at Safeco Field. He struggled through three innings, throwing 81 pitches while surrendering two hits and two runs, walking four and striking out six.
He was placed on the 15-day disabled list the following day.
Bedard, acquired from the Orioles in February 2008 for five players, including two eventual All-Stars, reliever George Sherrill and outfielder Adam Jones, has a 5-3 record and 2.82 ERA this season. He has walked 34 and struck out 90 in 83 innings.
He was 6-4 with a 3.67 ERA last season.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.