Of all the signings made by Erik ten Hag at Manchester United, this is the one hardest to rate. If Lisandro Martinez is perhaps Bruno Fernandes‘ biggest challenger for the most popular signing post-Sir Alex Ferguson, if Andre Onana has been hit-and-miss and Antony an expensive disappointment, then how do we describe Altay Bayindir‘s time at Old Trafford? The £4.3 million goalkeeper snapped up from Fenerbahce last summer has only played once. Against fourth-tier Newport County in the FA Cup, no less. Despite being highly regarded behind the scenes by Manchester United‘s coaches, if Martinez has…