Thibaut Courtois has told Sky Sports that Chelsea must maintain their "focus, ambition and hunger" if they want to challenge for the Premier League title.
The Blues are back on track under Antonio Conte after a disappointing 10th-place finish last season, but Courtois is cautious about naming them as challengers.
"We could be title contenders but after last season we have to be careful about everything," he said.
"We cannot relax because maybe last year we went too easy into the season because we were champions the year before. We have to keep the focus, ambition and hunger to win and, if we keep that, then maybe in May we can lift that trophy.
"The clean sheets are nice but, apart from against Leicester and Manchester United, I didn't have too much work to do. That's part of the teamwork. If you defend well you keep clean sheets and that's what's happening with Belgium and Chelsea."
Courtois, who is expected to start for Belgium in their World Cup qualifier against Estonia on Sunday, also dismissed worries about his bloodshot eye, a condition that has led to reports it could affect his game.
Everything's ok with my eye, had it for 2 weeks and doesn't effect my goalkeeping ������
- Thibaut Courtois (@thibautcourtois) November 9, 2016
"After the Manchester United game I came home and got sick," he said. "I had to vomit a few times and you force yourself, and it was just a vein that popped in my eye.
"It looks scary. It was the Halloween period so then it was OK but now it's not going away. They said 10 days and it's already been two-and-a-half weeks but it doesn't affect me in the game.
"Some pictures look worse than it is. There's nothing to do about it."