Left guard Mike Iupati suffered a sprained MCL when teammate Frank Gore ran into the back of his left knee Sunday in New Orleans, according to a source with knowledge of the injury. Iupati left the game in the third quarter and was carted into the locker room. Adam Snyder finished the game at left guard. Iupati had an MRI on the knee today. His prognosis is unknown at this point, but he is likely to miss at least Monday's game against the Redskins. If that's the case, it will be the first time one of the 49ers starting offensive linemen has missed a start since the beginning of the 2012 season. Snyder is the favorite to start in Iupati's place, although Daniel Kilgore has filled in at times during the offseason.