Rafael Nadal [Images] said on Monday he expected to lose his world number two ranking to Serbia's Novak Djokovic by Wimbledon at the latest.

Nadal's defeat by Juan Carlos Ferrero in the second round in Rome last week, when he was suffering from a badly blistered foot, coupled with Djokovic's victory in the final, means he could even slip to number three this week in Hamburg.

The Spaniard had a great claycourt season last year -- losing just once, to number one Roger Federer [Images] in the Hamburg final -- and then went on to reach the final at Wimbledon.

Having so many points to defend leaves Nadal vulnerable and the 21-year-old knows he has no margin for error between now and Wimbledon.

"Djokovic is very close, there's no doubt about that," Nadal told reporters on Monday after his arrival at the Hamburg Masters.

"I think, no I'm certain, that the logical thing is that he goes past me here, gets to number two here or at Roland Garros or in Wimbledon.

"He's a great player and he's doing things very well. If I'm number three I'm number three. When it happens I just have to accept it and fight to get the position back."

Nadal has complained repeatedly and bitterly about this year's ATP calendar, which has three claycourt Masters Series tournaments, plus Barcelona, crammed into four weeks.

His early defeat last week may have been a blessing in disguise and he said on a sunny day in Hamburg on Monday that he felt far better physically than he had going into Rome.

"I'm better," he said. "I'm still not perfect but I've had a few days off, and I'm much better than I was in Rome.

"I just hope the weather stays nice and hot."

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