Carlo Ancelotti admits Chelsea's clash with Manchester City on Sunday would prove decisive in their Premier League season.
But defeat would surely kill off their title chances and would also put qualification for next season's Champions League back in serious doubt.
Ancelotti said: It's important we win to clarify our position in the table.
"At the moment, our position is not so clear. After this game, it'll be clear what we're going to do in the Premier League."
The same could be said for City, who arguably must also win on Sunday to keep their dwindling title hopes alive.
And they have every reason to think they can, having proven to be Chelsea's bogey team since Ancelotti took charge, winning their last three games against the Londoners.
"I don't remember this," Ancelotti joked.
"I think that all three games we lost on counter-attacks. City will try to do the same now.
"They are very dangerous on the counter-attack, so we have to avoid this and maintain good balance on the pitch."
City boss Roberto Mancini became his fellow Italian's nemesis towards the end of the pair's time in charge of AC Milan and Inter Milan, respectively, and has now won five of the last six head-to-head clashes between them.
"He's a very intelligent coach who prepares a tactical game very well," Ancelotti said.
"That's the reason I have difficulty against him. I hope to change that on Sunday."
Ancelotti and Mancini have a friendship dating back to their playing careers.
"We were team-mates in the national team - he's a friend," Ancelotti said.
"Not such a friend because he's won too many times against me.
"He has to understand that he is my friend, so sometimes he can give his friend something."
With Chelsea and City boasting the biggest-spending owners in English football, Ancelotti and Mancini are arguably the most under-pressure managers in the country.
Ancelotti said: "This is normal, managing that pressure, for the coach.
"It's one of the skills a coach must have in football.
"The second thing is to be patient, not just with the players but with the club and the journalists.
"It's a good skill to have, patience, a very good skill."
His latest in a long line of problems is the goal drought being suffered by record signing Fernando Torres, who has now gone six matches without scoring since his £50million move from Liverpool.
Didier Drogba has also failed to find the net for nine games but Ancelotti revealed that was nothing compared to the famine endured by Hernan Crespo while he was in charge of Milan.
"I kept Crespo for six months without him scoring," the Italian said, reiterating he did not demand that his strikers find the net.
"I never said to them, 'You have to score'. The team has to score.
"The strikers are involved because they're closer to goal, but it's important they work well, move well and open the space for the midfielders."
Torres will be handed another chance to break his duck on Sunday but Ancelotti refused to reveal who would partner the Spaniard.
David Luiz will regain his place at the heart of defence after being cup-tied for Wednesday night's Champions League last-16 second leg against FC Copenhagen, meaning Ancelotti must decide whether to rest Branislav Ivanovic or switch him to right-back.
