Nadal opens the year ranked No. 4 but a knee injury kept him off the court of the second half of 2012 and a stomach virus has already led him to withdraw from the Australian Open -- where he was the 2012 runner-up.
The No. 4-ranking to open the year is the lowest for Nadal since he burst onto the tennis scene in 2005. He started that year No. 51 and, after winning 11 tournaments (including his first French Open), climbed to No. 2. He's started either first or second each year since.
He's just 185 rankings points ahead of David Ferrer, who is the top seed at the Qatar Exxon Mobil Open this week. Nadal has a 2,010-point edge on sixth-ranked Tomas Berdych, the No. 1 seed in Chennai, India.
Murray, ranked third, will be looking to keep his 1,310-point advantage over Nadal at the Brisbane International, where he is defending champion.
Djokovic is No. 1, a position he's held for 62 weeks, which is 11th most in ATP history.
Djokovic has 12,920 points while Federer is second with 10,265 and Murray has 8,000 for third. Nadal has 6,690.
Ferrer's total of 6,505 is fifth-most with Berdych (4,680) in sixth and Juan Martin del Potro (4,480) in the seventh spot. Jo-Wilfried is eighth with 3,490 points followed by Tipsarevic (2,990) and Gasquet (2,515).