England reached World Cup semis yet midfielder did not play a minute. But he is key to Manchester United in derby It was a sight the England press pack became increasingly used to seeing after the team’s World Cup matches over the summer. Kobbie Mainoo was invariably the first to leave the dressing room, walk through the mixed zone – eyes dead ahead, features impassive – and board the bus. It was as if he could not get out of the stadiums quick enough and the further England progressed the more…