Rafael Nadal says he does not think he will be able to knock Roger Federer off the top of the world rankings for at least a year.
"I'm convinced that if Federer keeps playing this well it will be impossible to catch him," said Nadal.
"I'm still young and I have to keep working hard so that one day I will have the chance to become number one.
"But given the circumstances at the moment being number two could hardly be better," added the Spaniard.
Federer has won eight tournaments in a superb year in which he has claimed three grand slam titles, taking his career tally to nine.
Nadal has won five tournaments, including a successful defence of his French Open title at Roland Garros where he beat Federer in the final.
He also reached the final of Wimbledon but was unable to stop Federer winning his fourth consecutive title in SW19.
"My aim is to play well at every tournament but, given what it stands for, the one I would really like to do well in is Wimbledon," admitted Nadal, who holds a 6-2 career lead over Federer.
The two could meet in the Davis Cup first-round match between Spain and Switzerland on 9-11 February.
However, neither player will commit to the match as they normally limit their appearances in the competition.
"I don't know if I'll play," said Nadal.
"Normally, I don't play the first round and at this moment I don't know if I will."