The Blues have recovered from the 4-0 defeat they suffered against Manchester United at Old Trafford on the opening weekend and are currently third in the table, eight points behind current leaders Liverpool.
Despite their sensational form, Mourinho is worried about how Chelsea will perform in big games this season.
He told Sky Sports: “In the first weekend I was worried and I’m still worried with the big matches. I think fantastic work. The kids coming into the team are fitting amazingly well with the top class players like Willian and Kante.
“I think really, really great work by Frank. But, they lost twice against United, they lost against Liverpool at home.
“They conceded four goals against Ajax and I’m very, very curious to see Chelsea in the next match at the Etihad.
“I’m curious to see if they found that great empathy between the good football they play and the pragmatism that the top teams must have to play against top teams.
“When they find that I think they have a great team for the future. I don’t believe in them to finish top two, but I believe very seriously for them to finish top four.”
