The Washington Redskins quarterback, who was named offensive rookie of the year in 2012, is a doubt for the start of next season after undergoing an operation to repair tears to two ligaments in his knee in January.
The team's head coach told reporters: "Robert is doing well, he's getting some great work in here, working out a couple times a day, about six hours a day, seven hours.
"He is ahead of schedule according to Larry [Hess, the team's head athletic trainer]. That means the muscles are stronger than they anticipated and he is doing everything he can to be ready for this season.
"Is he going to be ready? I have no idea. I'm sure keeping my fingers crossed. And if work has anything to do with it, he probably will."
The 23-year-old led the Redskins to the NFC East title and the playoffs during his first season with the side.