Woods made his return to action at last week's WGC Bridgestone Invitational, his first outing since limping out of the Players Championship in May.
He finished in a tie for 37th place at Firestone and will be looking to improve on that in Atlanta.
Donald, 31, who fared better in Ohio by finishing tied second, said: "It would surprise me if he went on and won the next couple of weeks.
"From what I heard, he found a lot of positives in his game [at Firestone] but obviously it's not where he wanted to be.
"He wanted to win. Getting back into that competitive mode is tough. It might take a bit of time."
The final major of the year begins tomorrow at the Atlanta Athletic Club.