Match statistics: Porto 0-2 Chelsea
After a tumultous week both on and off the field, Thomas Tuchel needed Chelsea's leaders to stand up and be counted against Porto on Wednesday.
Mason Mount may only be 22 and not even two seasons into his top-flight career, but there is no doubting that he belongs in that group.
All the England international's critics who believed he was being given preferential treatment under Frank Lampard have been made to eat their words since Tuchel's arrival.
If anything, Mount has taken his game to a new level under the German tactician, and no more so was that evident than in Seville - the neutral city chosen for Porto's home leg amid Covid-19 concerns in Portugal.
With Chelsea having come under increasing pressure in the first half, Mount picked up the ball near the right-hand corner of the Porto penalty area.
From there he produced a superb turn to stun Chancel Mbemba, leaving the ex-Newcastle defender for dead before arrowing a finish across Agustin Marchesin into the bottom corner.
After 32 minutes, that was Chelsea's first shot on goal in the the tie. When everything is added up come full-time at Stamford Bridge in six days, it will likely prove to be the decisive moment across the whole 180-minute affair.
It has been a Champions League week that has, in part, been defined by midfielders, both young and old.
Seasoned campaigners Toni Kroos and Kevin De Bruyne oozed class as they drove Real Madrid and Manchester City, respectively, to first-leg wins, while the next generation of English midfielders, Phil Foden and Jude Bellingham, shone in opposition at the Etihad Stadium.
For all his talent, Mount is rarely mentioned as either having the potential to reach the levels of the former pair, or possessing the talent of his younger compatriots.
And yet, after scoring his first Champions League goal, it is clear that the Chelsea academy graduate belongs at this, the highest level of European football.
No player has scored more for the Stamford Bridge outfit under Tuchel than Mount with five, and his performances now look set to earn him a starting berth for England at this summer's European Championship.
Those who called him out being overrated mere months ago are looking more ridiculous with every week that passes.
For all its importance in the tie, Mount's moment of glory proved only to be brief respite for Chelsea on the night, as they were forced to soak up a lot of pressure from Sergio Conceicao's side.
Many felt Porto were the weakest team left in the draw, but they at least showed in their performance here that their win over Juventus was no fluke, with Edouard Mendy and the defenders in front of him holding firm to keep out an attack that was missing its two primary goalscorers in suspended duo Mehdi Taremi and Sergio Oliveira.
As it was, the tie may now be over after Ben Chilwell joined Mount in breaking his Champions League duck and making the score 2-0 with five minutes left on the clock.
As West Brom showed on Saturday, scoring numerous goals as the visiting side at Stamford Bridge is possible, but Tuchel and his team will likely feel they have one foot in the final four as they settle in for their flight home.
That defeat to the Baggies, as well as the training-ground bust-up between Antonio Rudiger and Kepa Arrizabalaga that followed it, threatened to undermine Tuchel's record-breaking start to life in the Chelsea dugout.
But with a European semi-final against either Real Madrid or Liverpool now within reach, things are moving in the right direction once more.
A lot of that is down to Mount, who must now be dreaming of emulating his own Chelsea heroes from 2012 in Istanbul come May 29.
