Big-serving Jo-Wilfried Tsonga crashed out of the Shanghai Masters on Wednesday, beaten by Japan's Kei Nishikori 7-6 (7/1), 4-6, 4-6.
The number four seed appeared to be on his way to a straightforward win when he stepped up the intensity of his game to seal the first set tie-break with the loss of just one point.
But world number 47 Nishikori, who needed courtside treatment on his back, broke Tsonga twice in the second set, levelling the match when the Frenchman netted with a forehand.
Nishikori, who has a poor record against top 10 players, produced two more breaks in the deciding set, taking advantage of an error-strewn performance by Tsonga and sealing the win on his third match point.
The defeat puts a serious dent in the Frenchman's bid to reach next month's ATP World Tour Finals in London. He came into the Shanghai Masters in eighth place in the race to reach the showpiece, featuring the top eight players of the year.
Third seed David Ferrer of Spain came out on top 7-5, 7-6 (9/7) in his second round clash with Canada's Milos Raonic.
Earlier, Juan Carlos Ferrero came from a set down in an all-Spanish tie to oust 16th seed Fernando Verdasco 4-6, 6-3, 6-2, breaking six times during a match lasting a little over two hours.
There was also a win for 12th seed Alexandr Dolgopolov of Ukraine, who overcame Spain's Albert Ramos 5-7, 6-3, 6-2.
Austria's 14th seed Jurgen Melzer lost in three sets to Colombia's Santiago Giraldo while Australia's Matthew Ebden beat America's Ryan Harrison in straight sets.
World number two Rafael Nadal was due to launch his title bid against compatriot Guillermo Garcia-Lopez, followed by Britain's defending champion Andy Murray against Russia's Dmitry Tursunov.
World number one Novak Djokovic, Nadal, Roger Federer and Murray have already qualified for the year-ending ATP finals.