Kingsley Coman delivered the most painful demonstration of what Paris Saint-Germain let go when they allowed him to leave for Juventus with his winning goal for Bayern Munich in August's Champions League final.
Just under two months on from Bayern's 1-0 victory over PSG in the Lisbon showpiece, he reiterated his point as Hansi Flick's men started their defence of the European title by brushing past Atletico Madrid.
The decision to sell Coman back in 2014 has long since stood as one of the most questionable decisions made by PSG during the Qatar Sports Investments era.
His time with Juve may have been brief but his subsequent progression at Bayern has left PSG's move to cut ties looking increasingly ill-advised.
The folly of PSG allowing a homegrown player to take his prodigious talents elsewhere was encapsulated by Coman's decisive close-range finish at Estadio da Luz.
And a day after world-record signing Neymar cut an ineffective figure in PSG's 2-1 home defeat to Manchester United, Coman provided further evidence with a sparkling showing in Bayern's 4-0 win over Atletico.
The France international was pivotal in putting Bayern firmly in command, opening the scoring in the 28th minute as he brilliantly controlled an exquisite outside-the-boot pass from Joshua Kimmich and side-footed beyond Jan Oblak.
He turned provider 13 minutes later, collecting the ball on the left-hand side of the box before keeping it away from three Atletico defenders and playing an off-balance pass across the area for Leon Goretzka to lash home the second.
That assist was one of four key passes by Coman, who finished his involvement with a majestic flourish.
Corentin Tolisso had put the game beyond doubt with an unerring long-range drive but Coman fittingly had the final say with a scintillating individual goal.
He picked up Thomas Muller's pass in a generous amount of space down the right and surged to the edge of the area, where he turned a helpless Felipe inside out and slid a cool finish into the far corner.
It was a goal that marked the 20th time Bayern have scored four or more in a game under Flick, the most of any team in Europe's top five leagues since he replaced Niko Kovac as coach in November last year.
Coman was immediately withdrawn after doubling his tally, an understandable move by Flick given the his obvious importance to Bayern, who face five games in the next 17 days, including Champions League meetings with Lokomotiv Moscow and Salzburg and a Klassiker with Borussia Dortmund.
Leroy Sane's recent knee setback and Serge Gnabry's positive COVID-19 test further highlight how important Coman is to Flick right now.
Bayern's startlingly routine midweek should give them renewed confidence they can come through that run top of the Bundesliga and Champions League Group A.
It will have also made for grim viewing in the red and white half of Madrid and, after another inspired display by Coman, it likely won't have been well received in Paris, either.