Kevin De Bruyne's sublime finish proved to be the difference between the two sides, as Manchester City extended their lead in the Premier League.
The Belgian's 70th minute goal was the only of the game, with Chelsea struggling to take their chances to level the clash.
"Sometimes he needs to do the service. He had many ball losses without any pressure, many ball losses in very promising circumstances, without any pressure.
"He had a huge chance so he is included in this.
"Of course we want to serve him, but he is part of the team and the performance up front, especially in the first half, we can do much, much better and we need to do much, much better. We had a lot of transition chances in the first half."
Tuchel's comments came after Lukaku missed a huge chance to give his side the lead in the first half, with the Belgian instead trying to tee up an offside Hakim Ziyech.
It was a crucial moment for Chelsea's title hopes, but even after letting the game slip to their rivals, Tuchel insisted his side won't give up on the trophy.
"We will never give up, we deserved a draw, it would have been a fair result but we don't have it. We have won games like this against City, that's the way it is."
De Bruyne thinks his former team have their work cut out if they are to still challenge City for the title.
After enduring a difficult spell at the London club earlier in his career, De Bruyne's goal on Saturday marked the fifth time he's scored against them since leaving the club back in 2014.
Following the match, the 30-year-old playmaker acknowledged just how hard it would be for them to catch his current side.
"They need to be almost perfect. There is another team (Liverpool) dangling there, so we need to keep momentum and win each game.
"We have been in this situation before and things can change, momentum can change but the team was focused on what we could do today.
"It was a big game and they came here with a good plan, they were tight defensively but we played a good game. It's nice to score and it was important as it was the only one. We knew if we won we would make the gap bigger."
Manchester City manager Pep Guardiola echoed the words of his captain post-match.
"In January no one is champion. We can think about Chelsea, and Liverpool have games in hand. If they win it will be eight points and eight points in January is nothing.
"I want to win games if we deserve it, and we deserved it. I like football to be fair so, while I was happy to win against Arsenal, we didn't deserve it. Winning when deserving feels better."
Guardiola is also confident his players won't feel the pressure, or allow complacency to creep in.
"I know them. We have been together for six seasons and most of the guys know how to celebrate the good moments and suffer in the bad ones, how to behave after all the games.
"They are going to hear people saying things that are not true, that it is over, but they know it is not over."