Twins manager Ron Gardenhire said Span told him earlier in the day he was sick, but he came to Target Field to see how he would respond to a workout. Span fielded fly balls and ran through drills.
"He went back in and wasn't feeling worth a flip," Gardenhire said. "He tried it out there and didn't feel good."
Gardenhire said Span spent time in the training room and would likely receive an IV. Span, who is hitting .286, has started 51 of Minnesota's first 56 games.
Ben Revere started Friday's game in center field in place of Span, the third time this season Revere has started there. Revere is hitting .307 through 23 games.
Darin Mastroianni started Friday in Revere's normal position in right field.
"We have some depth back there in the outfield," Gardenhire said. "It's nice to be able to have some people you can put out there."