Spanish winger Mata is convinced that the Blues have finally stopped the rot with back-to-back wins against Newcastle and Valencia.
Now he aims to inflict City's first Premier League defeat of the season at Stamford Bridge.
Mata said: "City are the leaders and are playing well, so we have the ultimate respect for what they are doing. But do we fear them? Not at all.
"At the moment City have a big lead but it is difficult to believe that they will keep winning every game like they have been so far.
"Even though we are now 10 points behind them, it's definitely not impossible for us to catch them. The title is not decided for another six months and if we can beat City it will give everyone a lot more confidence."