And speaking of revenge, that brings us back to United's reunion with a certain Zlatan Ibrahimovic.
The 39-year-old left Old Trafford in 2018 and many thought he was finished after a double ACL tear in his penultimate season in the Premier League.
Since then, he's been banging in the goals for LA Galaxy and more recently, Milan - he's got 15 in just 19 games in all competitions this season.
Ibrahimovic had a happy stint with the Red Devils, winning three trophies (Jose Mourinho counted the Community Shield, so we are going to as well) and scoring 29 goals.
So who at United would the striker possibly want to get revenge on? Eric Bailly, of course.
The centre-back loved to wind up Ibrahimovic during their time together in the north-west.
In 2017, before the final whistle blew on the Europa League final victory over Ajax, Bailly could be seen shouting on the touchline and swinging Ibrahimovic's crutches around (the forward missed out on that showpiece due to his aforementioned injury).
But their best encounter came in the dressing room.
Even when he was injured, Zlatan was a huge influence around the club and so he was still lurking around even while undertaking his rehab.
Bailly posted a video on Instagram showing him kicking the Swede - in jest, of course - and then running away screaming when he came after him.
"Hope you're almost ready to return, @iamzlatanibrahimovic, I'll be right here!" Bailly wrote.
Watch out Eric, he's coming back for you!
When Ibrahimovic moved across the Atlantic and wrote a farewell message on Instagram thanking all his teammates, Bailly simply replied: "F*** offffff". Brilliant.
Ole Gunnar Solskjaer will have to hope he's fit for what is one of the tougher ties United could have been handed.News Now - Sport News