He's not a very good defender. Shows glimpses of decent defensive ability but his positional awareness is genuinely awful and he is constantly at fault for either individual or tactical defensive errors (part of this is down to Martinez's set-up but nowhere near as much as some claim, he's made many mistakes which are solely his fault and had no relation to the defensive system he played in). Honestly, I wouldn't bother with him, but if any manager will improve him it's Mourinho. If he comes here under Jose he'll do well. If he goes anywhere else (and realistically City is probably the only other option) he'll definitely flop imo. That being said, there's only interest in him because he's English and would meet the home grown quota. This would be a far greater concern at Chelsea than at United. Varane, Marquinhos, and Manolas, all of whom we've also been linked with, are far superior centre backs. Not saying he wouldn't work out if we sign him, he probably would, but there is far better value for money, and there is far better ability available too. Despite his injury concerns, Varane would still probably be my first choice. Manolas would be a good back-up option. Marquinhos could struggle to adapt to the Premier League but I do rate him. Ultimately, I think Stones is the most likely though. If that is the case, I hope we sign another cb also to alleviate some of the pressure that would be on Stones.