The Dodgers also recalled lefty reliever Luis Avilan from Triple-A Oklahoma City and placed right-hander Casey Fien on the DL with elbow tendinitis
Ryu made only one start for the Dodgers after returning from left shoulder surgery, throwing 4 2/3 innings and allowing six earned runs against the Padres on July 7. Los Angeles has not announced who will replace him in his start Wednesday against the Nationals.
"After he threw his 'pen Sunday it just kind of flared up, so we had to put him on the disabled list," manager Dave Roberts said. "There's really no timetable for him to pick up a ball or return."
Fien, who has a 4.09 ERA and a 1.182 WHIP in 22 innings out of the Dodgers' bullpen this season, felt his elbow tighten up during his outing Saturday, Roberts said. He will be replaced in the 'pen by Avilan, a lefty specialist who pitched in 23 games for Los Angeles in 2015 and appeared in six this year, allowing three earned runs in three innings before he was sent down.
The Dodgers have been hampered by injuries all season, but they just seemed to be getting healthy, with Pederson coming off the DL and pitchers Alex Wood and Clayton Kershaw expected to follow.
Despite the injury to Ryu, the team should benefit from the return of Pederson, who had a .328 on-base percentage and a .476 slugging percentage, along with 13 home runs, before getting injured last month.
Shortstop Corey Seager was out of the starting lineup for the second straight game Tuesday due to a stomach virus.
"He came in today and didn't feel well, we had him go back to the hotel, rest up, get some fluids in him," Roberts said.
Roberts said the rookie might come back to the ballpark depending how he felt, and could be available to pinch-hit.
Alex Putterman is a reporter for MLB.com based in Washington. This story was not subject to the approval of Major League Baseball or its clubs.