Jose Mourinho admitted he is worried about falling further behind leaders Manchester City but insisted his side have time to cut the eight-point gap.
Mourinho's Manchester United dropped further off the pace after slumping to defeat at Stamford Bridge.
The United boss said: “We are worried (about the gap).
"But there are 18 teams more worried than us because we are second.
“Eight points, in the Premier League, is not the same as eight points in the Portuguese league, La Liga, the Bundesliga.
“Eight points in the Premier League, there's still a lot to play (for).
"I hope, I feel, I think, I wish that in the busy period of late November, December, beginning of January, I think probably we are going to be at our maximum strength with Paul Pogba, Marcos Rojo and Zlatan Ibrahimovic back, with everyone who has been missing for the last few months, so probably we can be in a high.”
Alvaro Morata was the Chelsea hero as he headed the winner from Cesar Azpilicueta's cross.
Morata had three shots on goal in the game and, up against three strong defenders, that represents a commendable return.
Lukaku's afternoon was distinctly less fruitful. The Belgium international had one effort at goal from outside the box, but the tentative strike showed a lack of real conviction.
Lukaku did not manage a single touch of the ball in the Chelsea penalty area throughout the match.
"I don't want to talk about stats,'' said United manager Mourinho.
"I'm happy with his effort, attitude and desire.'