The Champions League resumes with a mouthwatering meeting of the aristocrats and the disruptors of European soccer.
The hosts: Real Madrid, the indisputable kings of the continent with 12 titles led by five-time world player of the year Cristiano Ronaldo.
The visitors: Paris Saint-Germain, the upstarts who bulldozed soccer's transfer record to hitch Neymar to the Qatari-funded mission to join soccer's elite.
The Santiago Bernabeu is the stage on Wednesday for Neymar's return to Spain six months after the heir to Ronaldo's throne was prized away from Barcelona for 222 million euros.
"(Neymar and Ronaldo) are both quick, very strong one-on-one, they play quickly and put a lot of intensity into their games," said PSG winger Angel Di Maria, a Champions League winner alongside Ronaldo at Madrid in 2014. "Ney is smaller, and that's perhaps his advantage. But they are both capable of turning games."
Only one of the superstars can advance from the round of 16 games in Madrid and Paris over the next month.
The 26-year-old Neymar is chasing the supreme status already attained by Ronaldo.
"He lives and breathes goals," Madrid coach Zinedine Zidane said of Ronaldo, underscoring the 33-year-old Portuguese's enduring influence on the team. Ronaldo has helped Madrid win three of the last four Champions League titles, with two goals in last season's final victory over Juventus.
Juventus helps to open the knockout phase this week against Tottenham on Tuesday when Manchester City travels to Basel. Liverpool is away against Porto on Wednesday but it will take something special to seize the spotlight from the Spanish capital.
It's not just a place in the quarterfinals at stake for PSG and Madrid. The losing coach is likely to find himself out of work by the end of the season.
Only two months ago, Zidane lifted the Club World Cup for a second successive year but his job prospects could be dependent on winning a third successive Champions League title.
So much has gone wrong domestically. Madrid languishes in fourth place and 17 points behind Barcelona in La Liga and is out of the Copa del Rey.
In Paris, Unai Emery is still haunted by last season's failures. He clung to power despite being deposed as French champions and an astonishing collapse at this stage to Barcelona.
"We're stronger than last season," Di Maria said.
Certainly in France where PSG has pulled 12 points clear of defending champion Monaco.
But while PSG can bully most teams, it is vulnerable against those playing with aggression and closing down high up the pitch. That was evident in a loss to Lyon last month when PSG panicked in defense and conceded a stoppage-time goal.
PSG will be hoping the decision to invest so much of its resources in securing Neymar and Kylian Mbappe does not backfire against Madrid.
Di Maria has been in stronger form than Mbappe recently, scoring four times in the last month compared to the 19-year-old forward's solitary effort.
Might it have been wiser to spend on protecting the shaky defense? For the trip to Spain, 32-year-old Lassana Diarra could be deployed as the holding midfielder even though Emery accepts he can't last a full game.
But Madrid has concerns in defense after conceding eight goals in its last five games, and Dani Carvajal is suspended after a yellow-card ploy backfired. While Carvajal had experience taking on Neymar in games against Barcelona, Zidane could be left relying on 19-year-old Achraf Hakimi.
Madrid is protecting a formidable home record in Europe, having gone 17 matches unbeaten. But as Karim Benzema has been discovering, playing at home has its pitfalls.
"I don't know why there's a section of our supporters that jeer Benzema," Zidane said. "His fortunes will change."
Here is a closer look at the week's other games.
Even though striker Paulo Dybala is sidelined with a muscle injury, Juventus can turn to Gonzalo Higuain who has scored six times in four matches. And he is likely to be leading the strike force with Mario Mandzukic, who netted in two of his three group stage appearances.
After an inconsistent start to the campaign, the back line has settled down and the Bianconeri have only conceded once in 16 matches in all competitions to set a club record. But the defense will be coming up against one of Europe's most lethal strikers in Harry Kane, who has netted 34 goals for Tottenham in all competitions this season.
While Juventus is slugging it out for the Serie A title with Napoli — they are separated by one point — Tottenham has a fragile grip on the fourth Champions League qualification place in the Premier League.
Since breezing through the group stage, City's quadruple chase has gathered pace.
Pep Guardiola's side has pulled 16 points clear in the Premier League despite Gabriel Jesus sustaining a long-term knee injury on Dec. 31. Sergio Aguero shouldered the burden as City's only other senior striker, scoring 13 times in 10 games across the league and two domestic cups — including four at the weekend.
Basel also has a tighter domestic title chase, sitting in second place five points behind Young Boys, and is adapting following the sale of center back Manuel Akanji to Borussia Dortmund in January.
Five-time European champion Liverpool scored 23 goals in the group stage, but has since lost playmaker Philippe Coutinho to Barcelona.
Shoring up the defense was a priority, though, in the January transfer window and center back Virgil van Dijk was finally signed from Southampton.
While Liverpool is 18 points behind City in the Premier League, Porto has a two-point lead at the top of the Portuguese standings and is unbeaten in 23 matches in all competitions.
Porto was the fifth equal highest scorer among the 32 group stage teams with 15 goals. But its leading attacking weapon, Vincent Aboubakar, is doubtful for Wednesday's match with a muscle injury.
STILL TO COME
The round of 16 is split over four weeks to suit broadcasters. The other first legs will be played next week. Bayern Munich hosts Besiktas, Chelsea takes on Barcelona, Manchester United is at Sevilla and Shakhtar Donetsk plays Roma.