Less than four months after being sold for just £5 million, Alvaro Fernandez is lighting it up at FC Benfica and rumours of a Manchester United return already abound. Alvaro Fernandez’ stunning Champions League form has thrust him into the spotlight this season and with Manchester United struggling at left-back, the irony couldn’t be clearer. Luke Shaw and Tyrell Malacia seem perpetually injured at this point and the last time United played with a natural left-back in the XI feels like a lifetime ago. Therefore, Man Utd’s Fernandez buy-back clause has been at the forefront of transfer rumours,…