Former Manchester City manager Roberto Mancini has said Manchester United need to overhaul their squad.
Mancini, now in charge of Galatasaray, believes United, who are 14 points behind Premier League leaders Arsenal, are suffering because of continuity and feels they have to make several signings.
The Italian believes City and Chelsea, who beat United 3-1 on Sunday, are outperforming the defending champions because they were more active in the transfer market.
He told BBC World Service: "Chelsea changed and bought some new players. City bought four or five new players. After many years, it's the time [for United] to refresh the team."
Mancini was supportive of new United manager David Moyes, who had an excellent record against him during his time at Everton, and believes he has a tough task replacing the retired Sir Alex Ferguson.
He added: "I think there is a good chance for him -- he worked for 10 years at Everton and he did a really good job. He is a good manager and I don't think he needs my advice.
"Alex was at the top but for every manager it is difficult [to come] after him."
Mancini was City manager from December 2009 to May 2013 and won the 2011 FA Cup, after beating United in the semifinal, and the Premier League in 2012, when his side finished ahead of their local rivals on goal difference.
But they failed to win a major trophy in his final year in charge and finished 11 points behind United.
Now, under his successor Manuel Pellegrini, City are competing for honours on four fronts and Mancini, who had a more confrontational approach, believes they are benefiting from a change of style at the top.
He explained: "When you work, you know you can have some problem with the players, but this is normal because the manager wants the players to work hard and play well and the players should understand this.
"When you bring in a new manager, it is better maybe, because you change the way they work."