Roger Federer suffered his first defeat before a final for 14 months when he was stunned by rising Briton Andy Murray 7-5, 6-4 in the second round of the Cincinnati Masters on Wednesday.
Murray, ranked a career-high 21st this week, became only the second player to beat the world number one this year as he broke the Swiss master's serve seven times.
The result meant it was the first time in 18 events that Federer had failed to reach a tournament final.
His last defeat before a final had been to world number two Rafael Nadal in the 2005 French Open semis.
Second seed Rafael Nadal defeated South Korea's Lee Hyung-taik 6-4, 6-3 for the second time in seven days to reach the third round.
The Spanish world number two produced the straightforward win in 80 minutes, breaking three times while never losing serve.
The double French Open champion earned an identical winning scoreline last week in the Toronto Masters against the 30-year-old Korean.
''My goal is improve on every surface, my goal is improve my game,'' Nadal told reporters. ''Not only on hard court but on every surface.
''But to improve on every surface, I need improve my game, that's the challenge.'' Nadal is keen to make an impact during the American hardcourt season following his third-round defeat in Toronto last week.
Although he has captured five titles this year, he has failed to get his hands on any trophy since triumphing at Roland Garros in June and is desperate to find some run of form before the U,S. Open begins on August 28.
Spain's Juan Carlos Ferrero outwitted American sixth seed James Blake 6-2, 6-4, while Australian Open finalist Marcos Baghdatis defeated Gael Monfils 7-6, 2-6, 6-1.
