The reason for the change is because Aston Villa's league game against Tottenham Hotspur has been brought forward to the same Friday evening, starting at 19:30 BST, and also being shown live on Sky Sports.
Spurs, like United, are hoping to reach the Europa League final, following a 3-1 first-leg win over Bodo/Glimt, and were originally due to play in the Midlands on the Sunday, at 14:15 BST.
The north Londoners have now been granted more time to prepare for any potential trip to Bilbao.