By Phil McNulty
Chief football writer
Manchester United's Champions League semi-final meeting with AC Milan is not just a contest for a place in Europe's greatest club game - it is a showcase for the sport's finest young talents.
KAKA v RONALDO
43---Games this season--47
15----Goals this season---21
Sir Alex Ferguson's attempt to claim the elite trophy for the second time in his career has centred on the brilliant form of Cristiano Ronaldo.
Ronaldo goes into the tie flush with success after scooping both the PFA Player of the Year and Young Player of the Year awards on Sunday.
Milan counterpart Carlo Ancelotti's bid to erase the nightmare of their 2005 Champions League defeat to Liverpool has been built around the emerging talent of Brazil's Kaka.
Bayern Munich's Owen Hargreaves, who played against Kaka in the quarter-final and is likely to be Ronaldo's Old Trafford team-mate next season, has no doubts about their pedigree.
He told BBC Sport: "Kaka and Cristiano Ronaldo are the best two players in the world at the moment."
The styles may be different, but the natural gifts and ability to change the course of a match in an instant are the same.
Ronaldo's tricks, feints and step-overs have finally been channelled into devastating end product - while the Kaka package is just as complete.
Hargreaves said: "Kaka is not really about tricks, but he is a fantastic footballer. He has great physique, a great touch, and fantastic technique. He is also a great finisher and a good header of the ball with excellent balance.
"Kaka also seems extremely relaxed on the ball and that allows him to use his attributes accordingly."
As well as lavish gifts, both players have displayed a strength of character that marks them down as special.
Kaka, 25 on Sunday, suffered a potentially career-threatening spine injury in September 2000 as a result of a swimming pool accident and was out of the game for a year.
To mention Ronaldo as one of the best players in the world is very soon. We have Kaka, who plays very well too
But he battled back and has flourished since joining Milan for £4.2m from Sao Paolo in 2003 - a fee described as "peanuts" by owner Silvio Berlusconi.
Real Madrid have long coveted Kaka as a prize addition to their Brazilian stars, but Milan have resisted all offers, knowing the damage his departure would inflict.
The Bernabeu giants endured similar frustration in their lengthy and very public pursuit of Ronaldo, who ended speculation by signing a new five-year contract at Old Trafford.
The 22-year-old demonstrated his resolve after returning from the World Cup ludicrously painted as the villain of the piece in Wayne Rooney's red card for England in their quarter-final defeat against Portugal.
Reassured by his mentor Ferguson, Ronaldo has ignored the taunts of opposition fans and finally turned all of his rich potential into a finished article.
Team-mate Patrice Evra describes his approach to the game in colourful fashion: "Nobody can stop him. Probably the only way to do it is to kill him.
"When he runs at you, you try to grab his shirt or do whatever you can. But he just goes past you, makes fun out of you and leaves you kicking the air.
"Even when he is sitting on a bike, Cristiano is doing tricks. He eats with the ball, he watches TV with the ball. He probably even sleeps with the ball."
Brazil great Pele is more cautious about the status of the two young stars, saying: "To mention Ronaldo as one of the best players in the world is very soon. We have Kaka, who plays very well too.
"Four or five years ago, we had Ronaldinho in good shape. We have to wait a little bit. Let's see, in one or two more years, if they keep at the same level."
The stage is set - and if either Kaka or Ronaldo produces the defining moment of a fascinating semi-final, even hard-to-please Pele might be convinced.