If you hadn’t been paying attention, you might be wondering why Manchester United appear to be in the market for a new left-back this summer. This, however, appears to be a pursuit borne out of necessity more than desire. Luke Shaw is not getting any younger, and could end the season with just 12 Premier league starts to his name. That is still 12 more than Tyrell Malacia, however, with Red Devils supporters expecting to wake up one morning and find the disappearing Dutchman’s face on the side of their milk carton. Harry Amass, a key part of the superb Manchester United U18 side which claimed …