England face a brutal test at the Riyadh Air Metropolitano on Sunday. World champions Spain stand in their way, unbeaten in a record 43 consecutive matches.
Spain had already beaten England in the UEFA Nations League at Wembley, but the Madrid rematch has become a decider for top spot in the group, according to Britain's Mirror newspaper.
Tuchel wants England to attack, backing themselves to beat Spain on their own merits.
It runs deeper than that, too. England need the belief to topple the very best, and to signal to the world that they can beat the big guns.
Tuchel said: "It is a huge stadium and an exceptional occasion. We will face a team that has forgotten how to lose, and that is why it first requires delivering a performance at the highest level, and if we succeed in that, it will give us a big morale boost."
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He added: "Victory cannot be considered inevitable when you play against Spain on their own soil, but I believe the mentality is extremely important. We won today, and that makes going into this match completely different from what would have happened had we not achieved the win."
He continued: "That was the first step, and now it is important that we play with the same mentality we showed at our stadium, that we take the initiative to attack them, and try to turn the match into a physical contest, while imposing our strengths on the opponent. That is what we want to see."
He went on: "No one can predict the result of a football match, but it is important that we show the mentality you are talking about, alongside the fighting spirit, and we will do that. I am completely confident in our ability to deliver this."
England had built a wonderful run at the World Cup before Argentina ended their hopes in the semi-final. The players dropped off, lost the initiative and surrendered the game.
Since then they have beaten France in the third-place play-off, lost 3-2 to Spain at Wembley, overcome the Czech Republic and thrashed Croatia 7-0 in Rijeka. On Thursday night at Wembley, they beat Croatia again, this time Slaven Bilic's side.
Tuchel reckons England have taken "big steps forward since the summer" and reached the final they were chasing. That turns Sunday into a huge occasion and piles enormous pressure on the players.
The German coach said: "We have to push beyond the limits of our abilities and find out where we really stand. We all feel we deserved a better result in the first match, and that is why we want to recover what we lost in the second encounter."
He added: "I believe we have reached the required level, and that we are ready to win on Sunday. I know what it takes to achieve that, and no one can guarantee the result at all, but I see it as the right moment to test how much progress we have made, to push beyond the limits of our abilities, and to prove that our project is capable of succeeding."
Spain's strength may be a worry, Tuchel admits, but it does not make them unbeatable. The last meeting at Wembley was level, and Harry Kane missed a penalty with Spain 2-1 up, a moment that handed England a genuine chance to fight back.
Tuchel went on: "It took us some time to get into the atmosphere of the match, and perhaps it was our worst start ever, after we conceded an early goal against a team with great confidence, but once we recovered our energy and began to play with the same power that led us to score the equaliser, we became stronger."
He continued: "We produced a very good second half, and it is strange that Harry missed the penalty, and perhaps that was the decisive moment for us, because we were very strong afterwards, and we deserved to lead 3-1. It was very difficult for the opponent to come back against us that day."
He added: "We made a large number of influential individual errors in our own half during that match, but if we look deeply at the matches, even Spain's matches, we will find that they made some decisive passing errors against Croatia, but were not punished."
He continued: "Spain allowed their opponent to create many dangerous chances against Croatia, yet in the end they managed to achieve the win, and that is why there is no team that cannot be beaten."
Tuchel concluded his remarks saying: "We need to deliver an exceptional performance, and we have great confidence and are constantly developing. I believe we have reached the stage we were aspiring to exactly, and we feel we have a chance to recover what we lost in the previous encounter."
