Former Manchester United defender Jaap Stam has slated one of Erik ten Hag’s first signings as ‘not good enough’ for the Red Devils. Erik ten Hag’s Manchester United have been busy in the summer transfer window as the Red Devils look to improve on last season. Just this week, United confirmed the double deal of Matthijs De Ligt and Noussair Mazraoui with the former Ajax pairing set to play a key role for the Red Devils this season. United have also signed Leny Yoro from Lille and have also improved their striking department with the signing of Dutch forward Joshua Zirkzee. However, former Unit…