Tuchel said: “We have the green light for N’Golo because we’ve had three days between games that make a huge difference.
“Mateo is unfortunately still out. He is feeling better, but can’t be in the squad. And Andreas Christensen is out and can’t be in the squad.”
Kovacic strained his hamstring in training this week, while Christensen has missed the last two games due to a knock, which he is still to recover.
Thiago Silva is back in the side after serving a suspension.
Tuchel has told his players to seize the moment against Pep Guardiola’s quadruple-chasing City.
“We are in a good moment,” he said. “We had a setback against West Brom, but we had an excellent response. “It’s a good moment to play City and Pep. They are, with Bayern Munich, the benchmark in Europe in my opinion. If we manage to beat Manchester City it will be a huge boost.
“If not we will have to take it as a challenge and opportunity to grow because we have big fights coming up. It’s not only about the FA Cup, it’s about the top-four race and the Champions League.”
Chelsea starting XI (3-4-2-1): Kepa, Azpilicueta, Silva, Rudiger, James, Jorginho, Kante, Chilwell, Ziyech, Werner, Mount