Nicks leads the Giants in receptions (79), receiving yards (1,052) and touchdown catches (11).
O'Hara missed nine games this season because of a Lisfranc injury in his foot.
The Giants listed several other players on their pre-practice injury report, including leading rusher Ahmad Bradshaw and safety Antrel Rolle with ankle sprains. Others included cornerback Corey Webster (ribs), defensive tackle Chris Canty (neck) and defensive end Justin Tuck (chest).
The Giants (9-6) need to beat or tie the Redskins in Washington and have the Packers (9-6) lose to the Chicago Bears in Green Bay to make the playoffs. A Giants tie, a Green Bay loss and a Tampa Bay Buccaneers loss also would put New York in the postseason.
The Associated Press contributed to this report.