Sunderland boss Steve Bruce will monitor the fitness of on-loan defender John Mensah for the rest of the season before deciding whether or not to make a permanent move for him.

The 27-year-old Ghana international has been hugely impressive when he has played for the Black Cats this season, and turned in a fine individual display to keep Manchester City star Carlos Tevez quiet last Sunday.

However, Mensah, who joined the club on a season-long loan deal from French side Lyon in August last year, has managed only 13 appearances to date because of a back condition which has led to a series of niggling injuries.

Sunderland's medical team have now come up with a fitness programme in order to manage the situation, and the defender has started the last four games on the trot despite training with his team-mates only on a Friday.

However, while Bruce has been left marvelling at Mensah's ability, he knows the fitness issue is a big one.

He said: "He has still got three years left at Lyon, so ultimately we will have a conversation when the time is right and we will just see what develops and see what happens from now until the end of the season.

"He is a very, very good player. The problem he has got is the ongoing problem with his injuries.

"But we have now got him into some sort of programme which benefits him. There's no disputing that he does tire badly in games, which is normal because he doesn't train a lot.

"But he can get away with it because of his natural ability. He is a fantastic defender.

"In the first half in particular against Tevez, he never gave him a kick; against [Fulham's Bobby] Zamora, he never gave him a kick.

"He is a fantastic player, it is just an absolute crying shame, the ongoing problems he has.

"But as a defender, he is unbelievable, superb, as good as you get."