Manchester United have twice been forced to field an outfield player in goal in modern times. Try as he might, Rio Ferdinand could not channel his inner-Edwin van der Sar and deny Sulley Muntari from 12 yards as Manchester United’s FA Cup dream died against Portsmouth back in 2007. John O’Shea, however, would enjoy a far happier time between the sticks. The affable Irishman kept a clean sheet after Van der Sar was forced off in a 4-0 win at Tottenham Hotspur a year earlier. And if United were to suffer a similar injury nightmare against Crystal Palace on Saturday, who would be against Noussair…