Manuel Pellegrini, the favourite to succeed Roberto Mancini as manager of Manchester City, has refused to talk about a move to the club.
Spanish champions Barcelona have agreed the signing of Brazil striker Neymar from Santos.
Ross Barkley has returned to Everton after the midfielder's loan deal with Leeds came to an end.
The youngster was not involved in the squad that lost 1-0 at Middlesbrough on Tuesday night, and he has now returned to Goodison Park.
"I spoke to David Moyes at Everton," United boss Neil Warnock told the club's official website. "He wants him to play and I couldn't guarantee him that.
"He's done well, he's a smashing player, but he needs to play games and I can't guarantee that."
The Everton youngster joined the club on January 11 and made four appearances during his short stay with the club.