Darnell said he will have an MRI exam on Friday morning. He suffered the injury attempting to make a leaping catch on a Tony Gwynn liner to lead off the sixth inning. The ball fell for a double.
Trainers and manager Bud Black attended to Darnell, who was on the ground for a couple of minutes before walking off under his own power.
"It didn't fully dislocate or anything like that," Darnell said. "The X-rays looked OK right now, but just have to see what the MRI says. It kinda locked up on me there."
Darnell said the injury is different from an injury he suffered last year on the same shoulder. He underwent season-ending arthroscopic surgery on Sept. 20 to stabilize the strained left shoulder.
"It didn't feel like last time," Darnell said. "Last time, there was a loud pop and a tingling numbness. This time, it was kind of like I jammed it or locked it in place."
Darnell was recalled from Triple-A Tucson on May 11 and has played in seven games, going 4-for-17 (.235) with one home run and one RBI. He made his Major League debut with the Padres last season, hitting .222 in 18 games.
Chris Denorfia replaced Darnell in left field. The Padres trailed the Dodgers, 5-0, at the time of Darnell's injury.
"James came up last year, we saw spurts of good play," Black said. "This year, he came up and looked much more comfortable.
"You feel for a guy, absolutely. He was swinging the bat well and playing the game."
The Padres currently have 10 players on the disabled list.
Sarah Trotto is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.