#4 Alejandro Grimaldo- Benfica

The patience with Luke Shaw seems to be running out as the Englishman has had constant fitness struggles and does not play with consistency. Left-back has been a serious issue for United over the years with Ashley Young past his prime and Shaw struggling to play. United need a new left-back and Alejandro Grimaldo would be the perfect solution for the Red Devils.
The Spaniard is a technically-sound and athletic left-back. His pace would make him a great attacking outlet without sacrificing defensively. United could convince Benfica for a good price for him and he would prove to be a great signing and an immediate improvement. Grimaldo would represent the opportunity to use full-backs more in attack, something which United really lack currently and increase the goalscoring opportunities for the attack.