"Nothing awful," manager Joe Maddon said. "He went through some tests, and it's just a bruise."
Maddon said the injury was minor and likely originated from a foul ball off Jennings' knee earlier in the season. He said Jennings has been cleared medically, might be available to pinch-hit Saturday and could start again as early as Sunday.
"Honestly, I think he might be ready tonight to help us," Maddon said Saturday afternoon. "He could be back at any time."
Ben Zobrist hit leadoff Saturday, Jennings' usual spot in the batting order. Kevin Kiermaier was slotted in center field, as he was Friday in Jennings' place.