Millwood's situation leaves Mariners manager Eric Wedge waiting on how he's going to play out his rotation during next week's homestand. The pitching is set through Sunday with Hisashi Iwakuma, Jason Vargas and Blake Beavan starting this weekend in Texas.
But the Mariners haven't announced their plans for the Orioles series beginning Monday at Safeco Field, with young right-handers Erasmo Ramirez and Hector Noesi already in the mix for extra starts as September callups.
Wedge has said Ramirez will likely get a couple more starts in the final three weeks after picking up his first Major League win Tuesday and Noesi will get at least one shot. Their availability makes it easier to hold Millwood back if he's not ready.
"He's about the same today," Wedge said before Thursday's series finale with the Blue Jays. "We'll have to give him a couple days before we decide what we're doing. Of course we have coverage here now with Noesi and Ramirez, so we'll be OK. But we'll give him some time to see how he feels and just go from there."
Millwood felt tightness in his shoulder early in Wednesday's start, which he wound up winning with his five innings of two-hit, two-run ball in the 3-2 victory. The 37-year-old said it's something he's dealt with before, but knew he couldn't keep pushing as he struggled to maintain his velocity.
"I think everything has hurt at some point," he said. "But that game was too close to go out there and try to be a hero or try to pitch when I didn't feel I could do the things I need to do."