The Dodgers are hoping Ryu can return to pitch Tuesday or Wednesday of next week against Arizona. Mattingly said he doesn't anticipate the injury being long term.
"We're not really concerned," Mattingly said. "Again, we're just being cautious, but no matter what the separation was [in the standings] right now, he wouldn't be pitching Friday. We would make sure he was right before he went out there."
Ryu slid awkwardly into home plate while scoring a run in Friday's game, which might have contributed to the injury. He threw in the bullpen before Tuesday's game and still felt tightness.
Ryu, a rookie of the year candidate who signed with the Dodgers in December after pitching in South Korea, is 13-5 with a 3.02 ERA. Capuano is 4-7 with a 4.50 ERA in 21 games.