The midfielder finds his Everton place under threat as well, with Koeman warning him to sort himself out.
Barry said: “I've been in that position myself. At Villa I had maybe two months out of the team. It coincided with being left out of the England squad.
“John Gregory was manager. It is really tough to take. It dents your confidence a bit.
“Ross isn't showing that. He just has to keep doing the right things.
“You only need one moment to turn your career around - a goal, a fantastic performance."