Manchester United boss Sir Alex Ferguson wants David De Gea to bulk up.

Spaniard De Gea, 21, has struggled since arriving from Atletico Madrid for £18million. Ferguson believes a slender frame is the root of his problems and is pushing him in the gym in an attempt to beef him up. The 6ft 4in De Gea weighs only 12st, two stone lighter than predecessor Edwin van der Sar.

Ferguson said: "The boy has got talent. He's lightning quick but has just found it difficult to adjust to some parts of the game here.

"It's a matter of developing his frame. He's doing a lot of work in the gym. If we can get maybe a stone on him without losing any of his flexibility or speed it would be a great boost to him."