What a difference one player makes. Lisandro Martinez is not only Manchester United’s best defender but arguably their best passer of a ball too. The most important cog in Erik ten Hag‘s machine, and the sort of infectious personality capable of grabbing his team-mates by the scruff off the neck – sometimes literally – and eking 10 per cent more out of everyone else in a Red Devils shirt. There is a reason why Pep Guardiola describes Martinez as one of the top five centre-halves in the world. Just look at the way Lisandro Martinez responded to Alejandro Garnacho‘s opener in Saturday’s glorious…