#1 Centre back

Chris Smalling and Phil Jones did a serviceable job at the tail-end of last season, but their deficiencies were laid bare in the FA Cup final against Chelsea, when Jones allowed Eden Hazard to run beyond him before giving away a costly penalty.
United's other centre-back options - Eric Bailly, Marcos Rojo and Victor Lindelof - aren't exactly bad, but the former two seem to have serious fitness issues, whilst the latter struggled to win round his new boss after a big money move from Benfica last summer.
When you look at Premier League winners over the last 10 years, virtually all of them were equipped with at least one world-class centre back. If the Red Devils are serious about mounting a proper title challenge this year, they desperately need to sign one of their own.