Rivera was injured Wednesday night. He is able to take batting practice and ground balls at first base, but has not worked in the outfield since pulling up on an infield single. He was tentatively scheduled to run the bases Saturday.
"He should be able to pinch-hit tonight," said Mattingly. "That's what we're hoping."
Mattingly said he would be more comfortable using Rivera at first base than in the outfield, but added that Rivera must be healthy enough to move around or there's no reason to play him.
"If [he's out] another day, we're getting closer down the road [to the DL]," Mattingly said. "But he's doing quite a few things for a guy with a hamstring [strain]."
The injury is where the hamstring connects to the knee. Rivera said the area had been bothering him before Wednesday night's game.