Real Madrid face a stern test in their defence of the Champions League, facing Paris Saint-Germain in the last 16 this week.
PSG and Madrid are two of European football's superpowers and one of them will be heading out before the quarter-final stage.
But who would feature in a combined XI made up of the respective squads? Is there room for Neymar, Cristiano Ronaldo, Gareth Bale and Edinson Cavani in the same team?
Here's our selection, using a 4-3-3 formation, but which club boast more representatives and whose head coach will be in charge?
In truth there is not a great deal of choice here, with PSG and Madrid both likely to attempt to upgrade their goalkeepers at the end of the season. Manchester United's David de Gea is a long-term Madrid target for good reason - Keylor Navas is not quite good enough for an elite club. But Alphonse Areola is no better, with the 24-year-old yet to be capped by France at senior level despite dislodging Kevin Trapp as PSG's number one this season. Navas therefore gets the nod, but this is a clear point of weakness for both sides that could be exploited during the two legs.
There is much stronger competition in the first of our four defensive spots, with Dani Carvajal and Dani Alves among the best right-backs in world football. Carvajal has been short of his best this season, though, like many of his Madrid team-mates, while his campaign has been disrupted by concerns over a heart condition. He is also suspended for the first leg, with Achraf Hakimi or Nacho set to deputise. Alves is a three-time Champions League winner and it is no wonder Pep Guardiola wanted to take him to Manchester City, as his huge personality is a massive boost in the dressing room. For that reason, and his combination with compatriot Neymar, Alves is our pick at right-back. He will certainly be up for facing Barcelona's arch rivals.
The two club captains make this a relatively easy decision at the heart of the back four. Thiago Silva has struggled with injuries but on his day the Brazilian remains one of the best out-and-out defenders in the game. And love him or hate him, Sergio Ramos has proven time and again he is a born leader for the big occasion. Ramos provides a massive goal threat from set-pieces and, although Raphael Varane's pace would make him a useful asset for our combined XI, Silva and Ramos effectively pick themselves here. They can wear the captain's armband for a half each.
Marcelo is another Madrid star who has failed to hit the heights expected of him in a stuttering campaign for Zinedine Zidane's men, but there is no doubting his quality and he offers a more consistent attacking threat from the back than PSG counterpart Layvin Kurzawa. The French full-back is capable of brilliance - witness his stunning volley against Lyon in Ligue 1 last month or his Champions League hat-trick versus Anderlecht for proof - but his season has descended into a scrap with Yuri Berchiche to be Unai Emery's first choice. The Brazilian flavour continues - Marcelo is our choice.
With three spots up for grabs in central midfield there are some big decisions to be made. A case could be made for Marco Verratti, who Barcelona have been keen on, while Adrien Rabiot has emerged as a defensive midfielder of real promise at PSG over the last couple of seasons. Casemiro's strength and positioning would also be an asset, although he is a walking yellow card, but we want to crowbar former Madrid man Angel Di Maria into the XI and this is where he is going to fit - adding more creativity to the team. Toni Kroos and Luka Modric have been two of the best midfielders in Europe for many years and it is impossible to ignore them.
Now we move on to the business end of the pitch, where there is an awful lot of competition for the three places across the front line. Gareth Bale has proven himself to be Madrid's most effective attacker so far this season - as well as their Club World Cup saviour - although the Wales star has had yet another campaign disrupted by injury. For PSG, the right wing where Kylian Mbappe usually finds himself squeezed into an all-star forward line, although the likes of Di Maria, Javier Pastore and Julian Draxler all represent fine alternatives. At his best, Bale provides explosive pace and moments of pure genius, so he is our first attacking pick. Let's just hope his troublesome calf holds out.
In any ordinary season, it would be ridiculous to leave Cristiano Ronaldo out of a world XI, let alone a combined selection between Madrid and one of their European rivals. But this has not been an ordinary season for the Portugal superstar. He may have collected his fifth Ballon d'Or but Ronaldo looked a shadow of his usual self until a recent burst of seven goals in Madrid's past four LaLiga outings. Neymar left Barcelona in a bid to become the world's best player and has been consistently brilliant, thriving on the left-hand side of the attack. There is more to do before he can be considered superior to Ronaldo but in a position favoured by both men, Neymar is our pick.
Karim Benzema has only scored two LaLiga goals this season, so it is very hard to build any case for his inclusion. The Madrid forward will surely be replaced at the end of the season, with Inter captain Mauro Icardi and prolific Tottenham striker Harry Kane reportedly among the names on the shortlist. Edinson Cavani has been banging them in again this term, usurping the great Zlatan Ibrahimovic as PSG's record goalscorer in the process. But Cavani still misses an awful lot of good chances and there is a suspicion that most decent attackers would thrive with Neymar, Di Maria and the rest supplying the ammunition. At this stage, we should probably cast our minds towards a certain weekend hat-trick against Real Sociedad. While his days of being an all-action tormentor of defences appear to be at an end, there remain few better at putting the ball on the big occasion than Madrid's main attraction. Rest easy, Cristiano, you've made the cut.
Madrid-PSG combined XI: Navas; Alves, Silva, Ramos, Marcelo; Di Maria, Kroos, Modric; Bale, Neymar, Ronaldo.
Emery has done reasonably well at PSG, but failing to win the Ligue 1 title last season is a stain on his record, regardless of how brilliant Monaco were. In this era, winning everything domestically is the least PSG expect given the untold riches that have been lavished on their squad. While Zinedine Zidane has not seemed his usual self this season, you cannot really argue with back-to-back Champions League titles in his first senior coaching role. It has to be Zidane, although the PSG tie may well decide the Frenchman's Madrid future.
Congratulations, Zinedine Zidane!— FIFA.com (@FIFAcom) October 23, 2017
Winner of #TheBest FIFA Men's Coach 2017 pic.twitter.com/fHTc3R1Q76