Defence promises to be a central issue for Carrick and Manchester United
- Carrick has private worries over United's five central defenders' durability
- No new centre-back signing planned unless a current player leaves
- Martínez is an injury doubt for the season-opener at Hull
Manchester United manager Michael Carrick faces a key test over the fitness and consistency of his central defensive options as he prepares for his first full season in charge, with the club competing on four fronts for the first time under him. Despite having five recognised centre-backs, Carrick…

