The German brought on N’Golo Kante for Mason Mount at half-time after growing concerned about his side’s performance against their fierce rivals.
It transformed the game and saw Chelsea run out comfortable winners and remaining level on points at the top of the table.
But Tuchel admitted he was unhappy with their first half display.
“We forgot to bring the right attitude and energy to this game,” the German said. “There were individual performances at a high level. For example, Thiago Silva and Kepa. But as a team, we allowed too many chances, way too many easy ball losses, not enough ball possession, and every 50-50 duel went against us.
“This had to change and, well, if you have N’Golo on the bench and you want to step up in these parts of the game, it’s the best player to bring on because he is unique and can change any momentum.
“For me it was clear they had another energy from us on the pitch like as a team they took risks. They played very aggressive and they played very brave. That opened chances for counter attacks for spaces for us because it was a very aggressive and very emotional Tottenham side in the beginning. But like I said too sloppy, not sharp enough to use this aggression.”
Chelsea quickly killed off the game with goals from Thiago Silva and Kante after the break – via a wicked deflection from Eric Dier.
Toni Rudiger completed the scoring late on.
“We wanted a higher intensity and work rate in our match to win balls actively and put the match in the opponent’s half,” added Tuchel. “Then we can rely on our skills, that was the idea behind it. The reaction was absolutely needed but we showed it and played a very strong second half to deserve this win.
“Second half was fantastic answer and very good performance.”