Federer's No1 reign under threat

Roger Federer's reign as world number one is under serious threat after losing to Ivo Karlovic in the Cincinnati Masters.

The defeat means that if Rafael Nadal can win the tournament the Spaniard will claim the world number one spot, ending Federer's record 234 weeks as the world's top player.
The Swiss player lost to 16th seed Karlovic 6-7, 6-4, 6-7, his 11th loss of the season, while Nadal progressed in straight sets against Tommy Haas 6-4, 7-6.
Having defeated Federer at Roland Garos and Wimbledon Nadal could have laid claim to being the best player in the world but can make it official if he wins Sunday's final.
"I know I'm in a good position. I don't think about it too much," Nadal said about the prospect of becoming world number one.