"It got to the point where, talking to Jedd and the training staff, we decided to give him a start off," said Padres manager Bud Black. "It's truly day to day."
"We hope he feels better quickly so we can get him back out there," Black said. "Hamstrings are tricky. With everyone, it's a little different."
Since returning from the disabled list on July 28 -- Gyorko missed 44 games with plantar fasciitis in his left foot -- he was hitting .291/.358/.488 entering Saturday with four home runs and 20 RBIs in 23 games and 86 at-bats.
Gyorko pinch-hit in the eighth inning Saturday with the bases loaded and struck out.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.