Quintero took a blow from L.A. shortstop Luis Maza's bat to the top of his helmet in the second inning.
Quintero was on the ground for three minutes, 58 seconds before being helped off by trainers and manager Cecil Cooper and was taken to Methodist Hospital for further testing. A CT scan performed at the hospital was negative, but he will be kept overnight for observation.
"It's really unfortunate," Cooper said. "He was playing very well for us, and his game calling has been much improved. He was starting to swing the bat for us a little bit."
Cooper said Quintero was groggy in the dugout as he was waiting for transportation to the hospital.
J.R. Towles will be recalled from Round Rock to replace Quintero. Towles, who was sent to the Express on June 5, is batting .288 in the Minors. Brad Ausmus replaced Quintero behind the plate in Wednesday's game.
"It's just bad luck," Ausmus said. "It happens. I had a concussion back in '03. It's just part of being a catcher. It's the hazards of the job."
Krysten Oliphant is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.Less