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 world number one's serve seven times.
It was the first time in 18 events that Federer had failed to reach a tournament final, his last defeat before a final coming against Rafael Nadal in the 2005 French Open semis.
Federer, who won the Toronto Masters Series event last week, complained his schedule was becoming too hectic.
"You've got to be a bit realistic. Winning back-to-back Masters Series, 12 matches in 13 days, it's just something impossible," Federer told reporters.
"If they don't start changing, maybe giving the seeds byes, I don't see any point why players should play back-to-back Masters Series anymore."
The eight-times grand slam champion, while sorry to lose after 55 consecutive match wins on North American hardcourts, took the defeat on the chin.
"You always expect a loss once in a while," he said. "When it happens, why be disappointed? I win over 90 percent of my matches. I would love that the streaks go on and on and on, but once in a while it's also good you lose."
Murray, in his third tournament under the tutelage of new coach Brad Gilbert, hoped he could build on the victory.
"Obviously this was pretty special - I wasn't expecting it to happen today," the 19-year-old Scot told British television.
"When you beat the top man it opens up the draw and hopefully I can make the most of that."
Murray now faces Robby Ginepri in the third round after the American 15th seed eclipsed Russia's Dmitry Tursunov 6-3 6-4.
World number two Nadal, however, sauntered into the third round and a match against Germany's Tommy Haas after a 6-4 6-3 victory over Korea's Hyung-Taik Lee.
Former French Open champion Juan Carlos Ferrero inflicted a comprehensive 6-2 6-4 defeat against sixth-seeded American James Blake, who has now won just three matches in as many tournaments since winning in Indianapolis last month.
Stanislas Wawrinka made up some ground for Switzerland when he beat third seed David Nalbandian 6-4 6-2.
Croatian fourth seed Ivan Ljubicic came through against Mikhail Youzhny 6-4 7-6 while Andy Roddick, last year's losing finalist to Federer, defeated Belgian Kristof Vliegen 6-4, 6-4.