Chelsea slumped to their second defeat of the season when Romeo Lavia and Adam Armstrong delivered a stunning first-half turnaround following Raheem Sterling’s opener.
The Blues have performed inconsistently across their opening five games, taking only seven points which leaves them in eighth and languishing off the top-four pace.
And Tuchel did not hold back with his assessment of their latest setback on the road, saying: “We are not tough enough to win these matches away. It was the same story in Leeds, there we thought the problem was we didn’t score in the first 25 minutes and then they pushed us off-balance in two minutes with two goals and we could not find any answers.
“Today, we scored so everything was okay but one set piece again, one sloppy defending again, we were off-balance and we did not react to it. We were lucky not to concede a third goal at the beginning of the second half. We were not tough enough as a team to react or push it over the line for us.
“Soft defending. What stops that is pure mentality, stop it with defending mentality. There is no superiority for the opponent, there is no need to give shots away, just toughen up as a team and show a different mentality
“I don’t like to talk about it normally because you cannot prove it with data or tactical position but it is like this. Both goals are cheap, soft goals and should not happen if you expect to win a match in the evening at an away stadium.”