Sunderland boss David Moyes says Manchester United forward Adnan Januzaj needs to "show more strength" during his loan spell at the Stadium of Light.
The 21-year-old, who has 18 months left on his United contract, was substituted in the 66th minute of Sunderland's 2-0 defeat at West Bromwich Albion on Saturday.
In the buildup to the game, Januzaj had said that United midfielder Paul Pogba wanted to play with him and asked the Belgian when he would be coming back.
Moyes, who managed United during the 2013-4 season, told reporters: "I know he is a really, really good footballer and wouldn't be out of place playing for many top teams, that is for sure.
"What I would say to him -- and have told him -- is that we need more from him. He is going to have to show more strength. He has great skills but, at this moment, he is finding it tough. It was competitive [on Saturday] but that's good. It can't always be games that suit him.
"Adnan has the ability to be a really top player but it is for him to show how good a player he is. He has a tough ask here but it will be a good education for him and part of building himself up."
The Scot also defended the player against claims that he is might not be showing enough commitment, saying: "Sometimes his body language gives you that feeling but, let me tell you, he is desperate to show people how good he is."