Federer falls again, could lose top ranking next week...

This is downright painful!

Roger Federer, one of the greatest players in the history of his sport, is in absolute free-fall and his latest loss will probably cost him his record-run at No. 1.

Defending champion Federer suffered a 7-6 (8-6), 4-6, 7-6 (7-5) loss to Croatia's Ivo Karlovic in the third round of the Western & Southern Financial Group Masters on Thursday. By failing to reach the semifinals, the Swiss star will see his streak of 235 weeks atop the rankings end if Rafael Nadal wins the title.