November 6 - Rafael Nadal will end the year as world number one after a victory over Stanislas Wawrinka in the ATP World Tour Finals at The O2 Arena.
It will be the third time the Spaniard has finished a year top of the rankings, having done it previously in 2008 and 2010.
He becomes the first player ever to hold, lose and regain the number one ranking on two separate occasions, with Roger Federer and Ivan Lendl each accomplishing the feat once.
His victory 2-0 over Wawrinka was his second win of the competition, having beaten David Ferrer in straight sets yesterday, and makes him the first player to secure his place in the semi-finals of the event.
The 27-year-old is looking to the win the ATP World Tour Finals title for the first in his career this week, having appeared in the tournament on five other occasions.
His best result came in 2010 when he made it all the way to the final before being beaten by Federer.
Nadal first achieved the number one spot on August 18, 2008, for a period of 46 weeks, becoming the first Spaniard ever to finish the season at the summit of men's professional tennis.
He regained the top spot from Federer on June 7, 2010, for another 56 weeks stretch, before losing out to Novak Djokovic following the 2011 Wimbledon final.
Nadal returned to the world number one spot on October 7 after reaching his 13th final of the season at the China Open in Beijing.
The accomplishment marked a phenomenal season for the Spaniard, who only returned to the game in February after seven months out through injury.
Coming back ranked number five in the world, Nadal won 10 titles, including the US Open and five ATP World Tour Masters 1000's, to storm back to the summit of the rankings.
He also went undefeated on hard courts - a run of 26 matches - before his loss to Djokovic in the China Open final.
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September 2013: Nadal powers his way to second US Open crown against Djokovic
February 2013: Nadal upbeat despite shock defeat in Chilean Open final
January 2013: Former World number one Nadal plans Chile comeback