"We think he'll play, but that's up to the doctors," Lynn said, per ESPN. "That's not my decision."
The veteran quarterback must be cleared by an independent neurologist before he's allowed to play again.
Rivers was placed into concussion protocol Monday following the Chargers' overtime loss to the Jacksonville Jaguars. It's unclear on which play Rivers sustained the concussion, but he was listed as a full participant in practice Thursday after being limited Wednesday.
Rivers, 35, hasn't missed a game since taking over the Chargers' starting role from Drew Brees in 2006. He has started 185 consecutive games, the second-best active streak behind draft mate Eli Manning (208) and the fourth-best all-time.
NFL Network Insider Ian Rapoport reported Wednesday that the Chargers were encouraged by the progress Rivers had made under protocol and there was optimism he would play Sunday. For a 3-6 team on the edge of falling into the abyss of another failed playoff bid, having Rivers under center could be vital for preserving the Chargers' postseason hopes.