DOHA, Qatar -- Ahead of Saturday's Clasico between Real Madrid and Barcelona, Xavi Hernandez has hailed Lionel Messi as the "greatest footballer ever" but believes that his former Barcelona teammate would not have reached the levels he has without Cristiano Ronaldo.

In an exclusive interview with ESPN FC's Andy Mitten, Xavi also paid tribute to Ronaldo and said that the two men have spurred each other to set new benchmarks in a sport which is at the highest level it has ever been.

"Pele and [Diego] Maradona both made a huge difference, but football has evolved," said Xavi. "The players are better than they were, the game is better. Physically, tactically, technically and psychologically, football is better than ever. And Messi stands out as the best at the best time in the history of football.

"But he wouldn't be as good without Ronaldo," Xavi continued. "He wouldn't have won all those Ballons d'Or. And I don't think Ronaldo would have won them all too. They push each other. The difference between the two is that while they're both great goalscorers, Messi is much more involved in the play of the team."

Xavi, who currently plays in Qatar for Al Sadd, was Messi's teammate at Barcelona for more than a decade and saw the Argentine forward mature during that time.

"He's become a man," said Xavi. "He's shy, but when he has your confidence and trust you see what he's like and he's a very good person. He's a joker, one of the biggest in the dressing room. He's witty, very ironic in his humour. He's intelligent and he's clever. Most of all, he's a winner."

Lionel Messi, left, and Xavi Hernandez, right, played integral parts in Barcelona's decade-long run of success. David Ramos/Getty Images

Messi has returned to training having been sidelined by a knee injury since Sep. 26, though his status for the Clasico remains uncertain.

In his absence, Barcelona have won five games out of six to move to the top of La Liga, which they currently lead by three points ahead of Real Madrid. They also top their Champions League group and Xavi, who admits he watches all of their games, has been impressed by his former club's recent form.

"They've reached a spectacular level without Messi," he said. "They have an intensity in defence, they press high, they give no time for the other team to think. Barca will win trophies again this season, I'm confident of that. Things are looking very good for the next games; I have a good feeling about them. It's a very, very good time."

Madrid, meanwhile, go into Saturday's game having most recently lost their first league game of the season, at Sevilla on Nov. 8. Despite that setback, Xavi insists they remain a formidable opponent and one which has become stronger defensively under new manager Rafa Benitez.

"Madrid are very strong this season," he said. "They are very organised with two lines of four. Physically, they're strong. People say that Benitez is defensive and yes, they've conceded fewer goals (seven) than any other team. But Madrid have also scored more (26) than any other team.