Serious illness has prevented Manchester United's Fletcher from playing since November.
"Darren will be with us at the weekend, he is back in training and he played 45 minutes in a practice match last week," said Levein.
"He is not in the squad because he has not played for Manchester United but he will come back and do a bit of training with us."
Last month Sir Alex Ferguson announced that he did not expect Fletcher to be fit for the start of the season.
Scotland face Australia in a friendly next week.