Ryu was injured while pitching Wednesday night in Atlanta. He threw a 3-and-2 ball to B.J. Upton and immediately summoned trainer Stan Conte.
An MRI examined by team physician Dr. Neal ElAttrache showed Grade 1-2 strains of Ryu's gluteus medius and piriformis muscles. The team recalled Pedro Baez from Triple-A.
Dodgers manager Don Mattingly said the timetable for Ryu's return is fuzzy because the injury is relatively rare, but he said the team is confident Ryu won't miss the remainder of the season and could help in its pennant race and the playoffs, if it qualifies.
"We feel good about this in the sense that it's not an elbow or a knee. It's a muscle strain, and it's going to heal," Mattingly said.
Ryu (13-6, 3.28 ERA) said Friday that, on a scale of one to 10, the pain in his strained muscles was a seven. He said he injured the muscle while planting and balancing his weight after delivering the pitch. He had felt some tightness in the muscle about four pitches before the one that caused him to leave the game. Ryu is listed as 6-foot-2, 255 pounds.
"I feel regret that I didn't take care of myself better and avoid something like this," Ryu said through an interpreter.
The Dodgers, whose starters have the best ERA in the National League, already had one, right-hander Josh Beckett, on the DL. The two replacements for the injured pitchers, Correia and Roberto Hernandez, were both acquired after the July 31 non-waiver trade deadline. Thus far, the Dodgers have received three quality starts from Correia and Hernandez.
"As long as those guys keep pitching well, you don't really think about it too much," Mattingly said.