Portugal coach Fernando Santos claimed Cristiano Ronaldo and Lionel Messi are “geniuses playing football”, as the prize pair prepare to face off tonight.

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All eyes will be on the duo when the Seleccao take on Argentina in a friendly at Old Trafford.

And on his return to his old Man­chester United stamping ground, Ronaldo will look to show just why he is tipped to retain the Ballon d’Or as the world’s best player.

“I voted for Cristiano because I think during the season he was the best player in the world,” said national team coach Santos. “We all know Messi is a good player and in my opinion they are two geniuses playing football.”

Defender Ricardo Carvalho, 36, has witnessed Ronaldo’s rise to greatness as a team-mate for Real Madrid and Portugal and said he could find no weakness in the front­man’s game, nor any hint of stop­ping in his pursuit of more trophies and accolades.

“He is doing a great job during this past six or seven years,” said the Monaco centre-back. “He is improving all the small details, making so many goals. He wants always more, even in training.

“Maybe next he can break his own records. He is looking always to try his best. He is almost perfect. He is strong, good in the air, good with his feet and he wants to win more and more. It is difficult to say what he is missing. He is the best.”

Having worked with his compa­triot at Barca, Argentina coach Tata Martino has a different opinion.

“You can’t take out of the decid­ing process I am Argentinian, my heart lies with Messi,” he said. “I cannot separate sentiment from my objective decision. Whatever season Messi had on footballing grounds, I would still vote for him.

“But yes I would vote for him on footballing terms [as well]. You can’t separate what he is like as a human from what he is as a player.

“I don’t see any change with Mes­si [from working with him at Bar­celona]. He is still the marvellous player he has always been.”

Martino may well try Messi again on the right of his attack as he looks to implement a style that will help them challenge for the Copa Amer­ica next summer. And United fans will also be hoping to see Angel Di Maria recapture his form, having faded after a stunning start.

Martino added: “Angel is one of the very, very top players in world football. The form he is showing now is more typical of going to a new club than his start when he did so, so well.”