Manchester United must beat Manchester City on Sunday if they want to keep their title hopes alive, according to Andrei Kanchelskis.
The Premier League's top two go head-to-head at Old Trafford in a pre-Christmas fixture that is about much more than just local pride.
City already sit eight points clear at the summit and a win over their neighbours would leave United with a mammoth deficit to make up, even with 22 games still to play in the campaign.
Kanchelskis - who played for both clubs during his playing career - feels Jose Mourinho's side simply cannot afford to lose further ground in their bid to be crowned champions for the first time since 2013.
"If Manchester United wins this derby game against Manchester City, they've a good chance to win the title," the former Russia winger told Omnisport, speaking at the signing of his book Russian Winters: The Story of Andrei Kanchelskis (deCoubertin).
"It's a must-win game. They [United] need the three points.
"It's a difficult few months over Christmas time, through December and January. There are too many games.
"There is the Champions League, the Premier League, the FA Cup, League Cup and possibly national team duties as well. That's too many, but we will see what happens.
"It [the derby] is important for both teams. If City drop points, there's a good chance for United in this race to be crowned champions. If they don't, it's difficult for United to win the title."
The derby sees Mourinho once again come up against Pep Guardiola, with the pair having previously locked horns at domestic level when they were in charge of Real Madrid and Barcelona respectively.
Kanchelskis admits Guardiola has City firing on all cylinders this season, yet believes this weekend's clash will help settle the argument over who is the better manager.
"Manchester City are playing good football. They are more attacking and have a lot of goal scorers," he added.
"But we will see in December who is best – Mourinho or Guardiola."
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