Koeman has vowed to point him in the right direction once again as he tries to get the best out of him.
Asked why he replaced Barkley at the break, Koeman said: "Because he didn't show the level I expect.
"I know it's always difficult for the manager because he was not selected for the national team and you take the player off after 45 minutes.
"But I had to do something. He lost too many balls. But I will speak to Ross tomorrow and that's no problem."