Tuchel was so concerned about the level of focus on the club record signing following his miserable display against Crystal Palace last weekend that he was omitted from the starting line-up in Tuesday’s Champions League clash.
Lukaku, who registered just seven touches of the ball at Selhurst Park, was an unused substitute as Kai Havertz and Christian Pulisic secured a 2-0 first leg win.
Tuchel explained beforehand that that striker was exhausted following his recent run of game, but later said: “Also it was not the moment after the match where everybody was focused on the few touches that we had to put him right into the next fire. It was the moment to take a step back. That was the decision and that’s it.
“You can clearly see we have a strong win and strong performance. It was a tough match and almost every question is about Romelu. The focus is huge.”
Tuchel added: “There were nine other players who did not play. We should never forget we consider this sport a team sport and the 11 guys who play do everything to commit fully to what we plan and to commit fully to their teammates and those on the bench have to do the same and this is how it works. Especially at Chelsea and especially for us and this is how we win football matches.”
Tuchel also made it clear Lukaku is struggling to adapt to the high-energy game he demands from his players.
He said: “The focus today was on intensity and a high-speed game. It was about hard work against the ball, off the ball and have intensive team work.
“Romelu struggled in the last few games a little bit to deliver that. That’s what I meant when I felt him a bit tired both mentally and physically.
“Since the Liverpool game, he started every match and there were some extra times as well. Yes, it is like this. Today, we went for three other players with Kai in great shape, very confident and giving a lot of work rate in high-intensive metres for the team.”
Lukaku is now a doubt to start Sunday’s Carabao Cup Final against Liverpool, but Tuchel refused to give anything away regarding his plans.
“The decision doesn’t need to be made today, but can be in the next four days,” he said. “He has every chance to play.”