'Chameleon' Ronaldo amazes Juve coach Allegri

TURIN: Juventus coach Massimiliano Allegri said Monday he was amazed by the extraordinary ability of Real Madrid superstar Cristiano Ronaldo to change his style of play in his thirties.

"I have to congratulate Ronaldo as a player at 33 years he's changing his playing style, it is something extraordinary," Allegri said ahead of Tuesday's Champions League quarter-final, first leg clash between the two teams in Turin.

Juventus defender Giorgio Chiellini believes Ronaldo could make the difference as he looks to build on a spree of 18 goals in his last 10 games for club and country.

"He's really crucial and can make the difference," said Chiellini.

"We all have great respect for Real Madrid, the fact that Sergio Ramos is the best defender in the world at the moment and Ronaldo is a wonderful 9.

"Ronaldo will always score against everyone. Real aren't just him, but over the years he's lifted them and makes the difference.

"It's presumptuous to think that you can mark him out of a game. We also need a little dose of luck, it comes down to certain things."

Real Madrid midfielder Luka Modric added that their chances of winning a 13th Champions League title were boosted by Ronaldo's form.

"He's a very self-confident person and in great shape. He's scored so many goals I've lost count. He's very important to have in the team and will increase the possibility of us winning and going through."

Meanwhile Real Madrid coach Zinedine Zidane conceded he has a selection headache with no major injuries and will have to choose between attacking duo Isco or Gareth Bale for the first leg.

"If Gareth plays, or Isco, it's the same, because they each contribute a lot," said Modric.

"Whether we play with one player or with another, the most important thing is that we run and we fight together.

"This season has been difficult for Bale because of the injuries he's suffered from, but now he's in good shape," continued Modric.

"He's managed to play good matches in succession, we know what we can expect from him in terms of performance."