France against Spain in Paris has the makings of a night to shape an era, or shake an empire. If the world and European champions lose away in Europe's Group I of qualifying for Brazil 2014 they would find themselves five points off the pace for the automatic chance to defend their World Cup title, with three group fixtures left.
Crisis? At the very least, Spain's current generation are unaccustomed to looking so vulnerable.
They must also recognise, quickly, the France side whose transformation since the quarter-final of Euro 2012, when La Roja out-passed and outclassed Les Bleus en route to winning the tournament, has been startling.
Only three of the outfield starters in France's 3-1 victory over Georgia on Friday, the result which put Didier Deschamps's team top of the group, were present in the XI who took on Spain in Ukraine only nine months ago.
It would be an exaggeration to talk of a revolution under Deschamps, but the presence of two debutants in key positions along the spine of the XI at the weekend has excited a French public whose relationship with the national team was damaged by the debacle at World Cup.
The Les Blues camp witnessed a player mutiny and subsequent bans on various alleged ringleaders in South Africa, and then by the flatness and indiscipline - Samir Nasri and Jeremy Menez were officially castigated for behaviour - at Euro 2012.
Raphael Varane, 19, and with an accomplished first senior outing for his country against Georgia to his credit, and Paul Pogba, just 20, are the conspicuous new faces.
Of Varane, Spain's players know something already. A Real Madrid player for the past two years, he has emerged as his club's first choice at centre-back this season. "He has unusual maturity for someone of his age," Deschamps said.
Pogba also is precocious. Signed by Manchester United at age 16, his pursuit of more regular midfield opportunities took him to Juventus last summer. At the Italian champions he is not yet an automatic first-team choice, but when he has played, he has impressed.
Deschamps has Yohan Cabaye, a more experienced man, back from injury to compete with Pogba for a role in central midfield.
But the manager indicated the choice between the two had become tougher because of Pogba's dynamic display against Georgia.
Pogba said: "I would love to play against Spain but a career is long, so I just have to keep progressing, if it's in the starting team or on the bench."
The strongest endorsements of Deschamps's first season in the job, though, come from his handling of players with troubled pasts.
Franck Ribery, one of those punished after the 2010 World Cup, has talked of the "liberation" he now feels representing France.
The man of the match on Friday, the short, stocky playmaker Mathieu Valbuena, is relishing playing for Deschamps.
The two were together at Marseille, where Deschamps worked before accepting the France post, and he had an uneasy, suspicious relationship with Valbuena for a period.
While France celebrates the youthful injection of talent, Spain confront the opposite sensation.
Their 1-1 draw at home to bottom-of-the-group Finland five days ago, coupled with the point France took from Spain last October, has made the serial champions of modern international football keenly aware the baton of excellence may not be passing seamlessly through generations.
Deschamps's counterpart, Vicente del Bosque, will draw optimism from the recall of Xavi, of Barcelona, and Xabi Alonso, of Madrid, both absent against Finland.
Xavi and Xabi carry the savvy of more than 200 caps between them into a midfield skirmish where Pogba may be winning only his second appearance in a full international.
Follow us @SprtNationalUAE