Fati is out of action with a knee injury, meaning that Coutinho is likely to be handed a starting place.
"He [Coutinho] can play in a lot of positions," Koeman said, refusing to give much away about his plans. "He's not a winger who goes deep. If he's on the wing, he'll move into the middle.
"He varies it. He's a great player and it's good that he can play in different positions.
"He has trained well and doesn't have any problems. He's been with the group for almost a week now. "We have to decide when is best for him to come in. We have to find the best plan."