San Francisco 49ers wide receiver Mario Manningham is done for the season after tearing the ACL and PCL in his left knee during Sunday night's 42-13 loss to the Seattle Seahawks, a source who has spoken with the player told NFL.com's Albert Breer.
Manningham had an MRI on Monday after X-rays on his knee were negative.
Manningham ranks third on the 49ers with 449 receiving yards on the season. The fifth-year pro out of Michigan missed two games earlier this month because of a shoulder injury.
He wasn't the only 49ers player to suffer a significant injury Sunday.