Antonio Conte's men suffered a shock 3-2 home defeat to Burnley in their opening match of the new Premier League campaign but have since bounced back with convincing victories over Tottenham and Everton.
The Blues goalkeeper has now give his assessment of Chelsea's opening three games and named the teams he believes will challenge for this year's title.
Courtois said, "the Burnley game was not good, even when we [still] had 10 men. We had a sloppy first half but the second half we were more aggressive and we transferred that into the game against Tottenham.
"They had better chances but we won and we needed to improve against Everton. We knew it would be a hard game but we handled it very well.
"Manchester United have started very well; City have bought in well and I think Liverpool showed [against Arsenal] they are up for the task this season.
"The Premier League is always hard and we will try to be there until the last day and see if we can retain it."