Manchester United legend Jaap Stam has backed the club’s newly appointed coach, Ruud van Nistelrooy, to challenge manager Erik ten Hag’s decisions at Old Trafford. He reckons that the former Manchester United striker will bring quality and experience to the club. United had, during the week, announced the appointment of Nistelrooy as assistant manager at Old Trafford. He replaces Mitchell van der Gaag, whose contract was terminated and the former striker will now work with Ten Hag. Jaap Stam warned that Ten Hag should be ready to have Nistelrooy challenge his decisions. “As a manager, you need…