Holders United will look to continue their trophy charge on all four fronts when they travel to Blackburn at 4.15pm.
Jose Mourinho's men have lost just one of their last 23 games in all competitions.
First up, Tottenham are at Championship side Fullham at 2.00pm.
The most recent meeting – a fourth-round tie in 2011 – ended 4-0 to Fulham, their biggest win against Spurs.
