"I don't know that," Donovan said Wednesday when asked if Roberson will be ready when the Thunder open the regular season next week, according to ESPN's Royce Young.
Roberson sat out all four of the team's preseason games and has been somewhat limited in practices.
"This guy hasn't done anything in a year and a half and we're thrusting him into a training camp," Donovan said earlier his week, according to The Oklahoman's Erik Horne. "We've got to give him some time to recalibrate, let his body heal, then come back and try to do some more."
Roberson suffered a ruptured left patellar tendon almost two years ago and has had setbacks since, including fracturing a bone in the same knee last November.
He's been one of the NBA's elite wing defenders when healthy. In 2017-18, the Thunder allowed 11.2 fewer points per 100 possessions (96.4) when he was on the floor, with the number soaring to 107.6 points with him on the bench.