As a player who relishes being centre stage, Cristiano Ronaldo will be in his element this week when the Champions League resumes with a blockbuster last-16 match between Real Madrid and Manchester United.

United transformed Ronaldo from a prodigiously talented yet hit-and-miss winger to one of football's most devastating goalscorers in his six years in the Premier League.

He has blossomed even further since his world-record transfer to Madrid in 2009, leaving United manager Alex Ferguson with the unenviable task of taming the player he nurtured into one of the world's most complete footballers.

Ferguson has been showering his former protégé with praise in the build-up to Wednesday's match and, as a self-confessed regular watcher of Madrid's matches, will have seen Ronaldo score a 20th hat trick for the Spanish giants in a league win over Sevilla on Saturday.

"(Zinedine) Zidane was a fantastic player, (Luis) Figo was a fantastic player but not as good as Ronaldo," Fergsuon said, comparing Madrid greats of the past decade.

"He's beaten all the records there. He's beaten (Alfredo) Di Stefano, (Ferenc) Puskas, Hugo Sanchez, all their records. He is indelibly printed in their history now. Ronaldo is pivotal to everything they do."

After a two-month break, Europe's top competition returns with three other last-16 first legs this week - Celtic vs. Juventus and Valencia vs. Paris Saint-Germain on Tuesday, before Shakhtar Donetsk hosts Borussia Dortmund on Wednesday.

All eyes, though, will be on the Santiago Bernabeu for the game between two of Europe's biggest clubs.

"It's a match the world is waiting for," Madrid coach Jose Mourinho said Sunday. "They are not waiting for other matches in the Champions League. So I hope we can give the world of football what they're waiting for."

Madrid's hopes of retaining the Spanish league title are almost over as it trails Barcelona by 16 points, and the widespread opinion in Spain is that Mourinho's job depends on the club winning Europe's top prize for a record 10th time.

"I think Jose has set his sights on the European Cup this year, there's no doubt about that," Ferguson said of his friend and rival Mourinho, who is bidding to become the first coach to win the Champions League with three different clubs.

United has no such worries domestically, leading the Premier League by 12 points with just 12 games left, so much of Ferguson's attention could also shift to Europe and adding to the club's haul of three titles in the competition.

Ferguson has won just two of his 14 meetings with Mourinho, with the two coaches now great friends away from the football pitch having initially had an uneasy relationship.

"I want to win and he wants to win," Mourinho said. "But I believe the loser, in the middle of being a bit sad, will have a little bit of space to feel a little bit happy because their friend has won."

Madrid's major injury loss is goalkeeper Iker Casillas, out with a broken hand, but United don't have any major concerns.

David Beckham - another Man United great - won't be making his return to Champions League action this week, despite being included in PSG's squad for the knockout stages.

The former England captain is expected to travel with the French team to Valencia but isn't fit enough to play in PSG's biggest game in Europe in more than a decade.

"He needs two weeks of training to be fit," PSG coach Carlo Ancelotti said Thursday about Beckham, who could therefore be available for the second leg.

PSG, the French league leader, is one of Europe's "nouveaux riches" and is looking to make its mark in the Champions League after spending heavily over the past two seasons under its wealthy Qatari owners.

New coach Ernesto Valverde has Valencia playing better than during its inconsistent start this season under former manager Mauricio Pellegrino, with the team having only lost one of its last seven Spanish league games.

Shakhtar Donetsk, which progressed to the last 16 at the expense of reigning champion Chelsea, may be rusty going into its home match against Dortmund as the Ukrainian league is in the middle of its winter break.

Former winner Dortmund, though, is also struggling after a 4-1 home loss to Hamburg in the Bundesliga on Saturday.

"Right now, I don't have any optimism in me," Dortmund coach Juergen Klopp said after the match.

Celtic will need to summon the kind of inspired of display it produced in beating Barcelona in the group stage when the Scottish team plays its first knockout match in the Champions league in five years.

Juventus is top of the Italian league, warmed up for the trip to Parkhead by beating Fiorentina 2-0 on Saturday and is unbeaten in European competition in 16 games.

- AP