Passing out of the back was another issue but dealing with direct, physical teams is going to be a constant issue for Utd while they have Maguire and Martinez at the back.
Maguire's issues aren't new. Throughout his time at Utd, whenever he's been asked to defend large spaces he's been a disaster because he's simply not quick enough or agile enough. And as Frank admitted, teams are going to target Martinez and the sheer volume of duals he's going to find himself in, the law of averages dictate that he'll be found out a few times, even if he defends well.