London (AFP) - After returning to the Premier League's top four, Manchester United have once again recruited extensively, but there are concerns about the balance of their squad ahead of the new season.Manager Louis van Gaal has spent around £77 million ($120 million, 110 million euros), notably bolstering his midfield with the additions of Bastian Schweinsteiger and Morgan Schneiderlin, to take his spending since succeeding David Moyes last year to around £230 million.With Robin van Persie and Radamel Falcao having left and Javier Hernandez out of favour, it leaves Wayne Rooney shouldering a heavy burden up front, but former captain Bryan Robson believes the midfield reinforcements can provide the platform for a first sustained title assault since Alex Ferguson's departure in 2013."The manager has built the midfield area to a point where we look strong enough to dictate the tempo of games," said Robson, now a club ambassador."Schweinsteiger and Schneiderlin look really good signings.