A's manager Bob Melvin said Andrus felt a pop in his ankle and was taken for X-rays.
"We won a game, that's good, [but] we may lose one of our toughest guys," Melvin said. "We've got our fingers crossed that it's not something significant."
Andrus singled to lead off the Oakland ninth, then scored without a throw on Starling Marte's double into the gap in right-center field when center fielder Jose Siri's throw back to the infield was low.
Andrus stumbled as he rounded third and fell onto home plate to score the winning run. He was checked by the training staff and had to be helped off the field.
Andrus is batting .243 with three homers and 37 RBIs this season.