"I don't think it's something that’s affecting my game," Lillard said, according to ESPN's Tim MacMahon.
The injury occurred in Game 2 of Portland's series against the Golden State Warriors, according to The Athletic's Shams Charania. Lillard's now wearing padding around his ribs, according to Sam Amick of The Athletic.
Head coach Terry Stotts admitted he wasn't aware of Lillard's injury until reports surfaced postgame Saturday.
"I didn't really know much about it until it became public," Stotts said, according to MacMahon. "Generally when he has something going on, he kind of keeps it to himself, so I would say it's not surprising."
Despite the injury, the Blazers guard played 40 minutes in Game 3. However, he was limited to just 19 points on 5-of-18 shooting, including 3-of-9 from 3-point range. Lillard also committed five turnovers.
The Warriors picked up a 110-99 victory Saturday to take a 3-0 series lead.