Rasmus, who aggravated a groin injury on Aug. 10 against the New York Yankees, was tested before batting practice to see if he was fit to play center field on Friday.
"Just waiting to see if Colby can go in center field defensively," manager John Farrell said Friday afternoon. "He'll run and test that out before BP begins."
When the lineup came out, Anthony Gose was in center field.
Farrell was asked if it might be easier for Rasmus to play left field instead of center as he returns from the injury.
"I'm not going to take someone who's been a center fielder and stick him in a new position when we're dealing with a short-term situation," Farrell said.
Rasmus was batting .245 with 20 homers and 66 RBIs entering Friday.