By David McDonnell Manchester United’s unprecedented success under Sir Alex Ferguson was built on a strong dressing-room culture. As much as their ability on the pitch, it was the standards set by United’s squad off it that enabled them to dominate English football for two decades. Erik ten Hag has worked hard to restore that culture of discipline to United, going in hard on players who step out of line or put their own interests above those of the team. As Cristiano Ronaldo and Jadon Sancho have found to their cost, Ten Hag has a zero tolerance policy when it comes to fragile egos, with both …