A knockout tie in the Champions League, in front of a packed house at the Santiago Bernabeu, pitting Cristiano Ronaldo and Gareth Bale against Neymar and Kylian Mbappe, is an occasion the football world is relishing.

But it is easy to see how Wednesday's last-16 first leg between Real Madrid and Paris Saint-Germain may fill coaching counterparts Zinedine Zidane and Unai Emery with a degree of dread, as both head into the Valentine's Day clash knowing the tie could serve as their last act for the respective clubs on the European stage.

It was tough to envision Zidane being in such a position when Madrid cantered to a third Champions League triumph in four seasons, becoming the first team to successfully defend the title in its current guise, with a 4-1 win over Juventus in the final in Cardiff last June. 

With that success following Madrid's dethronement of Barcelona in LaLiga, Zidane - already a popular figure among Madridistas after his successful playing career - appeared to be the rarest of things at the Bernabeu, an untouchable coach.

His reputation was only furthered when Madrid brushed aside Barca over two legs in the Supercopa de Espana. However, the prospect of Zidane being relieved of his duties has grown ever more likely in an extremely underwhelming 2017-18 campaign. 

Madrid have stumbled badly in their defence of LaLiga, not helped by the disappointing form of Ronaldo, and sit 17 points behind Barca, having also been knocked out of the Copa del Rey by Leganes.

Success in Europe is Zidane's last hope. Such disappointment has rarely been tolerated in Madrid, regardless of what has gone before. Carlo Ancelotti was dismissed just a year and a day after delivering La Decima and a third successive European triumph is perhaps Zidane's only way to avoid the same fate, though a similarly desperate coach stands in his way.

PSG are poised to reclaim the Ligue 1 title in dominant fashion, have reached the Coupe de la Ligue final and the quarter-finals of the Coupe de France, though Emery can be considered fortunate to be in position to lead them to such glories.

It would have been fair to expect Emery to be axed after PSG's meltdown in their 6-1 loss to Barca at the same stage of the Champions League last year but, despite a season in which they lost the domestic title to Monaco, the Spaniard was backed in incredible fashion in the transfer market as Neymar - the architect of their demolition in Catalonia - was lured from Camp Nou in a world-record €222million move and Mbappe arrived from Monaco in a loan switch set to become permanent at the end of the season.

They have formed a fearsome attacking trio with Edinson Cavani that has run roughshod over Ligue 1, but those signings were made strictly with the Champions League, the trophy PSG's Qatari owners have long craved, in mind.

As such, failure against a Madrid team seemingly a long way off the standards they set in recent years will undoubtedly lead PSG to cut ties with Emery, although the Spaniard may be allowed to see their domestic dominance through to end of the season.

Punishment for defeat is likely to be much more swift for Zidane, and may even come if the first leg does not go their way. Madrid's hierarchy and fanbase are similarly unforgiving and, with three weeks between the two legs, it would be no surprise to see Los Blancos look to another coach to turn the tie around in Paris.

An inability to win the Champions League would spell the end for either Zidane or Emery but, in the short-term, it is Zidane's job that is under greater threat and a home defeat to PSG could lead to the conclusion of the France great's relationship with the club to which he has given so much.