Robert Griffin III and Chris Clemons suffered serious knee injuries during their teams' playoff game on a shoddy surface at FedEx Field last season.It's tough to know whether bad sod influenced either injury or to what degree.The Washington Redskins apparently don't want to take chances. The team plans to upgrade the surface at FedEx Field in June and replace it after a Nov. 3 game against San Diego -- three weeks before the San Francisco 49ers visit for a Monday night game Nov.