Catcher Blake Swihart also sprained his left foot on a slide into the third-base bag in the fifth inning and was pinch-hit for in the sixth. He was 2-for-2 with a run scored before leaving the game.
"Both day-to-day," manager John Farrell said. "We'll check them when they come in in the morning. Undetermined right now if we're going to need to make a move."
With one out, Lorenzo Cain sent a hopper to Sandoval, who reached over in a unsuccessful attempt to catch Alcides Escobar off the third-base bag. When Escobar didn't budge, Sandoval turned and overthrew to first base, extending his leg and crumpling to his knee in obvious pain.
Sandoval rose after a few minutes and seemed to try walking it off before returning to the dugout under his own power. Travis Shaw replaced him at third.
"I thought he still had a shot," Farrell said. "It's a one-hop play that his momentum was taking him into the runner. He tags him, tried to correct himself, and deliver a throw across the infield, but I think if he makes the throw on line, he's got a chance to knock down the out."
Both players underwent X-rays, which Farrell said did not indicate fractures or any structural damage.
"It's pretty sore right now, but I'll be fine," said Swihart, who also said he didn't foresee a trip to the disabled list.
"That's not my decision, but it's just sore, that's all."
Jordan Wilson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.