Mateo Kovacic has been ruled out of Chelsea’s FA Cup semi-final against Manchester City on Saturday.
The midfielder suffered a hamstring injury in training on Monday, which meant he had to sit out the Champions League quarter-final with Porto.
Chelsea progressed to the semi-finals with a 2-1 aggregate win after Mehdi Taremi’s late strike for the Portuguese champions, and will face either Real Madrid or Liverpool for a place in the final.
Following the game, Tuchel confirmed Kovacic is almost certain to miss out again at Wembley.
“It was very sad to see him [on Monday] after 20 minutes in training, to have this little muscle injury from more or less out of nothing,” said the Chelsea manager.
“We played in the boxes for the second day after training, just to have a little sweat and he felt his hamstring.
“So I think, for sure, for the game against City he is out, it is a big loss.”
Tuchel added: “I was very sad for him because we don’t have so many experienced players that have played Champions League many times.
“If you see him when the anthem is playing and he stands there, you see him relaxed and at the same time he is a hard fight, everybody is happy to have him around. So we also did it for him today.”
N’Golo Kante came through the full 90 minutes in Seville and Tuchel is hopeful the Frenchman will be able to play from the start against City despite only just recovering from a hamstring tear.
He said: “We took the risk because we know that maybe this was the moment. Maybe it was not a risk, but the situation and put him on the field and hope he had the energy for 90 minutes.
“N’Golo is incredible, he is like one and a half or two players. Everybody who sees him for the first time loves him, all my family love him when they watch our games now. It’s so nice to have him.
“He wins so many balls, he gives everybody confidence and at the same time, like I said, we also did it for Kova.
“We were not sure if N’Golo would start today if we had everybody available but also, it was perfect. Now it is time to recover.”