Daniels was delivering information to the booths when he apparently slipped and fell nearly 30 feet to the loge level below the press box.
Medical crews performed extensive CPR on Daniels and managed to rescusitate him. Daniels, who was taken to Sharp Memorial Hospital, is reported to be in or around his 60s.
"He was breathing with a pulse and a heartbeat when he left the stadium," said Bill Johnston, a Chargers official. "We're waiting on further word."
The Associated Press reported that Daniels appeared to suffer a head injury.
The press box was sealed while police investigated the scene. Clean-up crews, including some wearing hazard material outfits, worked to sanitize the area where Daniels fell before gates opened to the public.
The accident delayed the opening of the gates by about 40 minutes.
Pedro Gomez is an ESPN bureau reporter. Information from The Associated Press was used in this report.