Sir Alex Ferguson insists Robin van Persie does not need a rest

Manchester United manager Sir Alex Ferguson has backed Robin van Persie to find his goalscoring form and insists the striker does not need a rest.

Van Persie, 29, has gone nine games without a goal for United.

But Ferguson is confident that the Netherlands international, who has hit 23 goals for the club this season, will soon start scoring again.

"He doesn't need a rest that's for sure, he's a strong lad with great physique," Ferguson said.

"The goals will come, all strikers have dry spells and you hope it ends quickly, it's part of being a striker."

Van Persie, who joined United from Arsenal for £24m last August, has scored 19 Premier League goals this season, second only to Liverpool's Luis Suarez, who has 22.

Premier League leaders United are 15 points ahead of second-placed City going into Monday's match.

Ferguson added: "It's a derby game with a difference from years ago. It's far more important. We have to get used to playing Manchester City in big games."