p]:text-cms-story-body-color-text clearfix”> Chargers wide receiver Quentin Johnston lays motionless on the field after taking a hit against the Rams.

Chargers wide receiver Quentin Johnston lays motionless on the field after taking a hit against the Rams.

(Allen J. Schaben / Los Angeles Times)

The Chargers got an early reminder of the perils of playing starters when, on the third play from scrimmage, receiver Quentin Johnston appeared to get knocked out after an incomplete deep pass. He took a helmet-to-chin shot from Rams safety Tanner Ingle and was knocked flat on his back, arms splayed at his side.

The game was stopped for several minutes as medical personnel attended to Johnston, who eventually was able to sit upright and instead of being wheeled off on a backboard rode off the field sitting up on the back of a utility cart. Johnston led the team with eight touchdown catches last season.

Harbaugh said after the game that Johnston sustained a concussion and was checked out at a local hospital as a precautionary measure.

“He was talking,” the coach said. “He remembered the play. He was moving good.”

Rookie receiver KeAndre Lambert-Smith, who has been having a great camp, didn’t wait long to take advantage of his opportunity. Two plays after Johnston left the game, “KLS” turned a completion and run into a 29-yard gain down the left side. Two plays after that, Herbert looked for the young receiver again, throwing a beautiful ball that grazed the fingertips of Lambert-Smith, covered tightly near the front-right pylon.

Minutes later, Taylor Heinicke threw an errant high ball for KLS across the middle and in heavy traffic, and the receiver couldn’t hang on. KLS did catch a shot, though, that sent him out of the game, although he returned to the field in the second quarter.

Ah, preseason.