Cristiano Ronaldo insists it is impossible for him to maintain the standards he set last season but has nonetheless vowed to recapture his best form in the future.

The Portuguese is expected to be named Fifa world player of the year later today following his stunning 42-goal performance in Manchester United's double winning campaign — for which he has already received the Ballon d'Or.

Ankle surgery delayed Ronaldo's start to the season and he has been criticised for his form since, with it suggested that the 23-year-old's desire to leave United for Real Madrid in the summer has left him unsettled.

But the winger claims the drop-off in his performance level was inevitable after the brilliance of last term and cites the likes of Kaka and Ronaldinho as other superstars who have failed to maintain their best form season after season.

"Tell me one player who had a great season for two, three, four years at the top level? It's impossible, you don't have anyone," said Ronaldo. "Last season I think I did brilliant but this season, in my opinion, I'm not bad, I've scored 10 goals up to now [he has nine in 23 matches], I've come in from injury and people are waiting [for me to get] better and better all the time.

"It is not easy but I know I feel in good form and I think Cristiano is coming better and better. If not this season, then next season I know I can do as well again."

The Liverpool striker Fernando Torres, Barcelona's Lionel Messi and Xavi and current holder Kaka have also been shortlisted for the Fifa award, which will be announced in Zurich tonight.