The 3-1 loss in the first leg of their quarter-final has left the European champions with a massive task to turn the tie around.
And Tuchel believes their performance at Stamford Bridge, which saw Karim Benzema score a hat-trick, has effectively killed off their defence of their crown.
The Chelsea manager did not hold back in his criticism and also claimed Romelu Lukaku’s missed header in the second-half could have proved the final nail in the coffin for his team.
Asked if the tie was still alive, Tuchel said: “No, not at the moment. No.
“We have to find our level back. I don’t know where it is since the international break. The first-half is a repetition of the second-half against Brentford in a quarter-final against Real Madrid. So far off our level in absolutely everything the game demands, we can’t expect a result from this kind of performance.
“I worry more about Southampton than I worry about Real Madrid in the next week. That is my focus. Today, is this alive? No, with this performance.
“If things change, maybe, but how many clubs in worldwide football won with three goals difference? How often did this happen? So maybe we should be realistic and should not get fatalistic and think that I give the wrong message.
“If we keep playing like this we will lose at Southampton and then we will get hammered at Bernabeu.”
Lukaku had the chance to cut the deficit with a second half header – but failed to hit the target from six yards out. Tuchel admitted that the miss could prove crucial.
“It was very important,” he said. “There are no more away goals so if we have only a one-goal deficit or a draw, then you see the momentum is back when we score.
“We could have even equalised. There were a lot of spaces and chances. But the individual decisions today were far from our level or standards.
“Yes, to come back with a chance like this at 3-2, after 16 shots in the second-half alone, then goals are crucial. We didn’t get them.
“We gave a third one away. It is simply impossible. We cannot demand that we turn it around if this is our foundation from this game.”