Manchester United qualified for the 5th round by beating Arsenal while Chelsea booked their place after defeating Tottenham.
Manchester United and Chelsea have been drawn against each other in an FA Cup 5th round encounter.
The tie will take place on February 15. Other ties will see either of Middlesbrough or Newport facing quadruple-chasing Manchester City, while League One Doncaster will welcome Premier League side Crystal Palace.
Both clubs now have different managers at the helm of affairs. Chelsea fired Antonio Conte who helped the club win the FA Cup trophy last season while Manchester United fired Mourinho last December.
Maurizio Sarri is yet to win any silverware in his managerial career, but has a great opportunity to change that this season with the likes of Liverpool, Arsenal and Tottenham already eliminated.