Manchester United can strengthen their grip on the top four if they can win at the Etihad on Sunday, and a victory would land a huge blow for Man City's title hopes.
Pep Guardiola's side are six points clear, but Liverpool have a game in hand on them. Lose to their rivals and it could be level pegging before long.
United are the current holders of that precious fourth spot, but have West Ham, Arsenal and Tottenham all breathing down their necks, and Wolves also in the hunt.
Ralf Rangnick will need to pick a side who can cope with the pressure City will put them under at the Etihad, in what will be his first Manchester derby.
The Red Devils have enjoyed a solid record at the Etihad in recent visits, winning twice there last season. Once in the Premier League and then again in the Carabao Cup, although they lost on aggregate in that semi-final.
Guardiola has only won one of his home Manchester derbies, with Ole Gunnar Solskjaer getting the better on several occasions.
Now Rangnick has been urged to switch to a back three to frustrate City, like other teams have done this season.
Arsenal legend Martin Keown told talkSPORT: "Solskjaer had a good record because he would often change his system to a back three, which is probably something Rangnick should think about this week.
"Although Rangnick has had a good seven days to prepare. I know he's trying to get that message across about pressing high through a 4-3-3 system, but I think it's ready-made to change because Maguire needs protection in the back three.
"It's not a given who the back three would be, or the wingbacks, but I do feel it's worth considering.
"Spurs beat them twice this season playing with a back five, maybe it's a problem for Man City. They are struggling to break teams down.
"Lots of teams are playing with a low block and it's quite difficult.
"Pep Guardiola has been reemphasising that he wants the ball moved quickly and wants that opening.
"It's quite difficult and you point to the fact they haven't got an out-and-out striker, and does that really matter. They've been so successful, but it does count sometimes.
"City got a bit lucky last week with the handball that wasn't against Everton, they got a bit of luck.
"I think when you are the hunter, it's better to be in that position. I was in that position when we chased Manchester United down, and we were chased down in 2003."
So how would Manchester United line-up in a 3-5-2?
If Rangnick wanted to switch to a back three, it would be a deviation from the 4-3-3 he has been playing in recent matches.
Maguire would get greater protection playing in between Raphael Varane and Victor Lindelof, while Alex Telles and Diogo Dalot would provide better attacking threats, and athleticism, as the wing-backs.
Scott McTominay was pictured back in training ahead of the derby and, if fit, should start with Bruno Fernandes and Paul Pogba either side of him.
United will need pace to hit City on the counter attack and Jadon Sancho is the perfect man for that job, in what will be his first game at the Etihad despite having come through the club's academy.
He will play alongside Cristiano Ronaldo because, despite the doubts over his impact at times this season, you surely can't drop one of the world's top players and a man for a big occasion.