City play host to league leaders Chelsea on Saturday looking to close the gap on Carlo Ancelotti's reigning champions.
Despite the season being only five games old, Cech believes that defeat for City this weekend could kill off their ambitions of winning the championship.
"If we can win this game against City, we will be 10 points ahead of them and that is a big advantage at any stage of the season," said Cech.
"We would regard that as a huge help in putting one of our rivals behind us for the rest of the campaign."
Cech has also warned big-spending City that money cannot gurantee success and that they have no more excuses if they do mount a serious title bid this season.
"You can buy all the best players in the world, have a great squad, great stadium, top manager and fantastic facilities," added Cech
"But money alone cannot buy success. You need spirit and atmosphere in the dressing room and in the club generally to make the team successful.
"It's down to the players at City to build that but, right now, they have more pressure on them to deliver than ever before.
"For the past two years, they've spent lots of money but everyone was prepared to say, 'City are in transition, it will take time'.
"Now they don't have any more excuses. They can't say, 'We have a lot of new players and need time to settle'.
"City have everything set up to win the league. Now all they need is some momentum on the pitch.
"We are starting a period of the season when the top teams have a lot of big games and you need the whole squad to be ready to play.
"Chelsea, Manchester United and Arsenal are all used to playing in these situations but City have never had to cope with it before, so only time will tell if they are serious title contenders this season."