Thomas Tuchel has admitted Romelu Lukaku was left isolated against Brentford and was subsequently taken off in the second half during the 1-0 win after looking tired.
The 28-year-old is now four games in the league without a goal as Ben Chilwell's brilliant strike in the 45th minute was the difference in the west London derby to earn the Blues all three points.
Chelsea were up against it. The Bees proved their top-flight credentials and made Tuchel's side work for their win as Edouard Mendy was called into action to make several world class saved to ensure it remained 1-0 in the capital on Saturday evening.
Lukaku's evening ended 13 minutes from time as Tuchel brought on Kai Havertz to see the game out.
Post-match, the Chelsea boss was quizzed on the Belgian who started upfront with Timo Werner which saw both draw a blank against Thomas Frank's team.
"I felt him a bit tired today," admitted Tuchel. "Altogether we did a very strong 60 to 75 minutes, including Romelu and Timo. I am not concerned as I felt him a bit tired and then isolated because we were defending as a block too deep.
"Both of them, Timo and Romelu, were too far away to help us and escape the pressure. That was the problem today. But I have no concerns.
"Normally, the best thing is he scores but he is very unselfish at the moment, looking for Timo in good situations, and when we had him in the situation it was a close offside decision."
More Chelsea Coverage
- Chelsea hold onto claim vital three points with 1-0 win over Brentford to move back to top of the Premier League
- The Chelsea player ratings as Edouard Mendy and Ben Chilwell help Blues overcome Brentford
- Five things we learned from Chelsea's narrow 1-0 win in west London derby against Brentford