All the talk ahead of kick-off in Saturday's FA Cup semi-final at Wembley had been about Manchester City's quadruple bid but by the time the full-time whistle had blown, Chelsea proved that they can beat Pep Guardiola's side.
And that's all down to one man: Thomas Tuchel.
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Before this fully deserved 1-0 victory, the German had never previously got the better of Guardiola as a coach.
When the pair had previously squared off in Germany, they were never quite competing on a level playing field, even after Tuchel had swapped Mainz for Borussia Dortmund. There was just no stopping Guardiola's Bayern Munich.
However, Tuchel has since moved on to bigger and better things, taking Paris Saint-Germain to a first Champions League final last year before being appointed as Frank Lampard's successor in January.
As at the Parc des Princes, Tuchel now has the resources to rival those of Guardiola at City, and he has now shown himself capable of making a major impression on English football.
He's already had a massive impact at Stamford Bridge, of course, losing just two of his first 19 games in charge of Chelsea. And just this week, he led his new team to the semi-finals of the Champions League, meaning the Blues could yet meet City again this season, with a European Cup on the line.
On the evidence of what we saw at Wembley, Chelsea would fancy their chances. Indeed, they were good value for their 55th-minute opener, which came courtesy of Hakim Ziyech.
For once, City were unable to hog the ball, with a confident Chelsea side claiming a 49.5 per cent share of possession during the first half.
"If you have good ball possession against City, maybe it is the best way to defend," Tuchel told reporters after the game. "But we were very strong in the defensive statistics too, and is down to the courage of the players, both as individuals and as a team.
"We defended very, very actively and aggressively, with huge solidarity. Everyone needs to attack and defend. That is the key."
Tuchel's approach certainly forced a tactical change on the part of Guardiola, who clearly instructed his side to press higher up the pitch after the restart.
No sooner had they moved their defensive line forward than Chelsea pounced, with Mason Mount releasing the lightning-quick Timo Werner, who crossed for Ziyech to tap home.
It was just the latest in a long line of clever tactical tweaks Tuchel has made since taking over, and ultimately decided the game in his side's favour.
It was a goal that also showed that Tuchel has a masterful hold of this squad, rotating effectively after a midweek aggregate win over Porto in the Champions League quarter-final.
It was after that match in Seville that Tuchel also opted to keep his players in the south of Spain for an extra night. They stayed in their bubble but took time out for some hard-earned team bonding.
He allowed them a drop of alcohol, a chance to let off some steam during the most pressurised part of the season.
Of course, not everyone has benefited from Tuchel's arrival, as underlined by Tammy Abraham's omission from the matchday squad even though the FA Cup allows a nine-man bench.
Still, there is no denying that star summer signings Kai Havertz and Werner have progressed under his leadership, while Christian Pulisic is also back on form.
There are plenty of homegrown heroes in the mix too, with Mason Mount, Callum Hudson-Odoi and Reece James all retaining prominent roles in Tuchel's team.
The bottom line is that, after just three-and-a-half months, Tuchel has shown that Chelsea are ready to compete for major honours again. With this win, he has already become the first German manager to reach an FA Cup final.
That he has achieved that little piece of history by beating Guardiola is arguably even more significant.
"It was an outstanding performance in all matters and all subjects of the game," Tuchel continued. "It is clear that we need that to beat the benchmark of the Premier League which is City. I am very, very happy we could do that and it was a deserved win."
Man City remain the best team in the Premier League, as the table proves. But Tuchel said on Friday that Chelsea intend to "hunt" Guardiola's team.
Saturday's victory proved they're more than capable of catching them.