If Manchester United’s last two performances taught us anything, it’s that the importance of one particular Red Devil should never be cast into doubt. The Premier League’s biggest underachievers picked up zero points out of a possible six without a certain star man, barely threatening the Crystal Palace goal in that one-sided 4-0 hammering before failing to turn their possession into a final-third threat as title-chasing Arsenal threatened to repeat that Sylvain Wiltord moment at Old Trafford on Sunday. They say ‘absence makes the heart grow stronger’. And if this is what life looks like at Ma…