Branyan, who leads Seattle with a career-high 31 homers, has been out since Aug. 29 with a herniated disk. He took batting practice Thursday and Friday and hit off a tee Saturday and Sunday because the Mariners did not take BP.
Seattle had hoped to get Branyan back sometime in the final week of the season, but manager Don Wakamatsu said Sunday it doesn't look very promising.
"It doesn't look real promising right now that he'll finish the year," he said.
Branyan also has played for Cleveland, Milwaukee, San Diego, Tampa Bay, Philadelphia and St. Louis in a 12-year career. He's batting .251 with 76 RBIs in 116 games this season.