Chelsea, on the other hand, have seemingly emerged as genuine title contenders after hitting the ground running under new boss Maurizio Sarri and go into the game level on points with Manchester City and Liverpool at the top of the table.
The Blues also boast a very impressive record against United in the Premier League era and would love nothing more than to pile further misery on their former boss this weekend.
Here, Sports Mole compiles a combined XI between the two sides, using only players in contention to feature on Saturday.
David de Gea's stock has fallen slightly since the end of last season given the struggles of Spain at the World Cup and United so far this term, but he is still probably the best goalkeeper in world football and is a relatively easy choice ahead of compatriot Kepa Arrizabalaga for the gloves in this team.
It is an all-Chelsea defence in front of him, though, with Mourinho having readily admitted that he is unsure about his own backline this season. Cesar Azpilicueta continues to provide consistent performances week after week - be it at centre-back or on the right - while Marcos Alonso has established himself as arguably the best attacking full-back in the league, a crown he does not look like giving up despite now being in a defensive four.
Antonio Rudiger is a doubt for this weekend, but should he be fit then he is the first-choice centre-back for this team, and David Luiz is well and truly back in the fold at Stamford Bridge now. The only real competition for United comes from Chris Smalling, with Eric Bailly and Victor Lindelof still failing to impress so far.
Jorginho has settled into Premier League life just as quickly as his manager, and his position in the middle of the park has pushed N'Golo Kante a little further forward - a move which has not affected his significant impact on matches. Former Chelsea man Nemanja Matic provides competition in midfield, but doubts over his fitness give the edge to Jorginho.
There is a United representative in the shape of Paul Pogba, though, with the Frenchman joining his fellow World Cup winner Kante in the team. Pogba has had his fallouts with Mourinho and has not always performed on the pitch this season, but there is no doubt about his ability.
Arguably the standout player of the season so far has been Eden Hazard, who has both scored more goals (7) and directly contributed to more goals (10) than any other player in the league, despite being rested in the opening weeks after his World Cup exploits.
With Alexis Sanchez, Marcus Rashford and Anthony Martial among the United players struggling for form at club level, Willian gets the nod on the other side of the front three, also beating competition from teammate Pedro for a place in the team.
Leading the line is former Blue Romelu Lukaku, who has failed to score in his last six appearances for United but did net twice for Belgium during the international break. Olivier Giroud and Alvaro Morata are also in contention, but despite his recent drought Lukaku is still the top pick out of the trio.