Sir Alex Ferguson has picked out Lionel Messi and Cristiano Ronaldo - rivals in next week's Champions League final - as the two most gifted players in the game.
The Manchester United manager believes the two stars' work ethic allied to their natural ability sets them apart.
Ferguson, who rates the quality in the Champions League as even higher than in the World Cup, also rates AC Milan's Kaka to an extent ''although he has never really taken my breath away''.
He told the latest issue of UEFA publication The Technician: ''There are some players, such as Kaka, Messi and Ronaldo who are innately gifted.
''But this is not enough, and there is a practice element which becomes very important.
''If you watch Cristiano Ronaldo, he practises after every squad training session, and quite a few others do the same.
''As a coach, we dedicate parts of the training to improving touch, movement, passing and speed of play, but the special quality, the detail, depends on the player being willing to sacrifice himself after training - this is a hallmark of the great players.
''If the big talents only rely on their natural ability, they won't have that extra edge. They must do something extra on their own.''
Asked which opposition players he rated highest, Ferguson replied: ''When I think of the current generation, Lionel Messi is top level and, although he has never really taken my breath away, Kaka has impressed.''
Messi and Ronaldo will come face to face in the Olympic Stadium in Rome, and Ferguson believes the Champions League is hard to beat when it comes to drama - even compared to the World Cup.
The United manager added: ''There are many good games at the World Cup, but in general the quality in the big UEFA Champions League games is, in my view, higher.
''I think that, overall, the UEFA Champions League is hard to beat when it comes to consistency, quality and drama.
''The World Cup, of course, is every four years, and big changes always take place with the departure of many players and coaches and continuity then suffers.''
Ferguson also picked out AC Milan's Paolo Maldini as his favourite opposition player during his time as a Champions League coach.
''He has a wonderful presence, competitive spirit, athleticism, and although not the world's greatest technically, he has influenced all the AC Milan teams during his wonderfully successful era - a truly marvellous player,'' said Ferguson.