The Spanish tennis star Rafael Nadal will head to the US Open as world number two after winning the Cincinnati Open.
He's overtaken defending champion Andy Murray, who's been named third seed for the final major of the year, starting in New York next Monday.
Roger Federer drops to seventh, his lowest ranking for 11 years.
Nadal is enjoying his best-ever run on hard courts, winning all 15 matches on the surface.
He now heads to New York looking for his second US Open title, and in position to go end the year as the world number one.
Murray has reached the final of the last four Grand Slams he has played, winning at the US open and Wimbledon, but he slips to three in the latest rankings.
Federer has fallen two places from fifth after a season in which he lost in the second round at Wimbledon and fell in the semi-final in Australia and quarter-final at the French Open.
He has lost a quarter of his 40 matches in 2013.
Novak Djokovic is the men's number one, while there is no change in the women's rankings with Serena Williams top ahead of Victoria Azarenka and Maria Sharapova.