Chelsea's 1-0 win over Atletico Madrid in Tuesday night's Champions League last-16 first leg in Bucharest confirms that the Londoners were right to sack Frank Lampard as manager and replace him with Thomas Tuchel.
The Blues have been transformed into a solid, well-drilled unit in under a month, and they passed their toughest test yet by out-thinking and outplaying Diego Simeone's Spanish league leaders.
As Tuchel told BT Sport afterwards, "We never let them breathe. We never gave them any chances to counterattack."
There's still a second leg to come, of course, but Olivier Giroud's stunning overhead kick has put Chelsea in an excellent position to reach the quarter-finals.
That the French forward started was something of a surprise, given the 34-year-old had been left out of four of Tuchel's eight previous line-ups, but Giroud once again proved that he is a man for the big occasion.
Indeed, Giroud had been Lampard's go-to man in this season's Champions League, too, having netted a crucial winner at Rennes on matchday three before scoring four in a stunning rout of Sevilla to seal top spot in Group E.
The former Arsenal forward's goal in Romania also means he now has 18 in Europe for Chelsea, which puts him behind only Blues legends Didier Drogba and Lampard on the club's list of all-time leading scorers in continental competition.
However, while Giroud will understandably dominate the headlines for his acrobatic winner, Tuchel deserves most of the credit for this victory - and not just for selecting the France international.
Since taking over, the German coach has done a fine job sorting out the Blues' backline, as underlined by the fact that Atleti failed to register a single shot on target in Bucharest.
Tuchel's decision to switch to a 3-4-1-2 formation has proven key and even Rojiblancos boss Simeone was full of praise beforehand for the impact his Chelsea counterpart has had in such a short time at Stamford Bridge. © Provided by Sporting NewsOlivier Giroud Atletico Madrid Chelsea Champions League
"They invested a lot in young players and, after they saw the investment didn't pay off, then they brought in Tuchel," the Argentine told reporters at Arena Nationala. "Since he came in, they have had a good change in their numbers."
Tuchel also deserves credit for the brave decision to drop N'Golo Kante and put his faith in Jorginho and Mateo Kovacic in midfield. However, Tuchel's early reliance on Mason Mount shows that he isn't just dismissing the previous manager's players to prove a point.
Even when Tuchel seems to have erred, it works out in the end. Callum Hudson-Odoi was visibly upset at being replaced just 31 minutes after coming on in last weekend's draw at Southampton but the youngster delivered a wonderfully mature performance at wing-back against Atletico.
Tuchel, it seems, can do wrong right now. The players are certainly happy with the fact that they are all getting chances to impress, while the board must be immensely satisfied with the fact that the new manager has propelled Chelsea back into contention for a top-four finish and now put them a positive result away from the last eight of the Champions League.
And what's remarkable is that all of this has been done while still trying to restore the confidence of potential superstars such as Timo Werner, Kai Havertz, Christian Pulisic and Hakim Ziyech.
Getting them firing is imperative, of course, as the next few weeks are massive for Chelsea, who face Manchester United and Liverpool to come in the league before taking on Sheffield United in the quarter-finals of the FA Cup.
Chelsea still hold huge expectations after investing £220 million ($275m) in the summer and they want a turbulent season to end in success.
They could well get their wish, though, as Tuesday's fully deserved win over Atleti underlined. Giroud's finish was spectacular, but Chelsea's Tuchel-inspired solidity was even more impressive - and far more significant.