McCarthy missed the defeat at Southampton at the weekend, despite having returned to training on Friday, and the boss hopes he will be fit for the games to come.
Koeman is hoping he will be fully fit this week and available for the next game, which is Manchester United next Sunday, ahead of home games against Arsenal and Liverpool to come next month.
"McCarthy stopped training after the first session (last) week. He was tired and had a little problem in his hamstring again," Koeman told the club's official website.
"He did not train Tuesday or Wednesday. He started training on Friday again and I didn't take the risk of putting him in the team (against Southampton) because we need everybody fit and available for the busy time coming up."