Bay was sidelined for a second straight day by a tight hamstring, though he normally wouldn't have faced right-hander Joe Blanton anyway.
"The plan was at least to give him a couple days," manager Eric Wedge said.
Help could be on the way in the outfield with Dustin Ackley working in center and left field at Triple-A Tacoma and Franklin Gutierrez eligible to come off the 60-day disabled list on Saturday if his sore hamstring continues to hold up.
General manager Jack Zduriencik was in Sacramento to watch the Rainiers the past two days and Wedge said reports on both Gutierrez and Ackley were positive.
"Jack saw [Gutierrez] last night and said he looked really good," Wedge said. "I know Gut says he's feeling normal, and that's a good sign."
Ackley is hitting .383 in 19 games since being sent down, but has only been working in the outfield for about a week now.
"Jack said he looks real good in left field," said Wedge. "He didn't really have any balls in center field, but he's been OK there, too. And he's swinging the bat, he's up there ready to hit. So he's doing what he needs to do down there, but we just need to give him a little more time in the outfield, whether in left or center.
"The reps in center would just be a concern right now. And I want to make sure what he's doing up there mentally at home plate is real as well."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.