Alex Ferguson warns Danny Welbeck he must score more goals for Manchester United

Sir Alex Ferguson has challenged Danny Welbeck to break the 20-goal barrier this coming season to prove he can be a top-class striker for Manchester United.

At the European Championship, Welbeck announced his arrival on the international stage by fending off Andy Carroll to become England's first-choice striker and start, beginning all four games in the Ukraine and scoring a spectacular winner against Sweden to double an England tally that began the previous month with a well-taken winner against Belgium.

Despite his international form, however, he faces a battle for a starting place at United, a fight he can only win by increasing his output from the 12 goals he scored last term, nine of which came in the Premier League.

"Danny can be a top player but obviously he will have to improve his goalscoring," said Ferguson. "He got nine goals last season but if you are going to be a top striker you have to get 20 or above. I think he will do that."

Brought up in the same Longsight district of Manchester as Wes Brown, United have taken a keen interest in Welbeck from a very early age. It is a good job too, as being under United's wing allowed him to receive more thorough treatment of injuries that otherwise might have halted his progress.

"He's always had growth spurts and little things like weak knees and weak thighs," said Ferguson. "It was happening all the time, so we fostered him from the age of nine right through that period when he was developing."

And Ferguson feels that Welbeck still has to complete that physical development. "He's not got his full body yet," said the manager. "There's a lot of growth in him yet. At 6ft 3in, I don't think he'll get taller, it will go the other way, and he is very powerful already. And he showed maturity at the Euros by playing three games in seven days, which he has certainly not done for us before."

If Welbeck headed off on his summer holiday buoyed by his international experience, strike partner Wayne Rooney failed to do himself justice at Euro 2012, missing England's opening two games through suspension, then producing below-par displays against Ukraine and Italy as the team lost in the quarter-finals.

Not that Ferguson was entirely surprised to see Rooney struggle. "I always thought it was difficult," said Ferguson."We know him better than anybody and he needs a lot of football. Wayne's a stocky lad. If he misses a couple of games, it takes him three or four to come back and he didn't play from his last game [for United] on 13 May until the third game of the Euros more than a month later."