It was a stiff left shoulder, the delayed symptom surfacing as a reminder of the cost of running into fences face-first at full speed.
That's what Kemp did in the first inning Tuesday night at Coors Field. Two batters later he came out of the game, passed a CT scan on his jaw and an MRI on his knee while taking three stitches to close a gash on his chin.
But like a car accident or similar trauma, new symptoms can present themselves 24 to 48 hours after the initial event.
"His knee feels pretty good, doing a lot more stuff, but his left shoulder is a little stiff and that's keeping him back today," manager Don Mattingly said. "I did the lineup tonight thinking he still had a chance to play. He did a lot to get loose and a lot of areas are really good. But the left shoulder didn't get loose."
Kemp didn't even mention the shoulder when he told reporters he was just trying to get the swelling out of his left knee.
"We'll see how it feels tomorrow," he said. "Just take it day by day. It's always frustrating. It's been a frustrating year, sitting out a lot of games. I'm used to playing every day, so it's frustrating when I can't play."
Kemp earlier missed 51 games with two stints on the disabled list with a strained left hamstring.
Shane Victorino again moved over to start in center field with Juan Rivera starting in left field.