The Giants batted around while scoring four runs on five hits in the first inning. Chris Perez replaced Ryu to start the second inning of what would become a 9-0 rout at the hands of their NL West rivals.
There was no immediate indication of the severity of Ryu's injury this time, though his velocity was down Friday night.
Ryu will be examined by team orthopedist Dr. Neal ElAttrache Saturday. The 27-year-old said it felt similar to the injury that kept him on the disabled list from April 28 to May 21 with shoulder inflammation.
"It's a little bit of everything, stiffness and pain," Ryu said through an interpreter.
"Obviously, you get one of your top guys and he's feeling something in his shoulder, at any point in the season you'd be concerned," Dodgers manager Don Mattingly said.
The Dodgers were leaning heavily on their top three starting pitchers to try to sew up the NL West, having scheduled Ryu, Zack Greinke and Clayton Kershaw to pitch 11 of the team's final 16 games, including all six against the Giants, but this could scramble those plans somewhat.
Ryu was 14-6 with a 3.16 ERA going into Friday's game. He also spent time on the DL this season with a right hip strain.