Gilles Simon shocked Stan Wawrinka at the Shanghai Masters, while Jack Sock broke new ground by beating Milos Raonic on a day in which Novak Djokovic and Andy Murray eased into the quarter-finals.
Unseeded American Sock reached the last eight of an ATP Masters tournament for the first time on Thursday, recovering from an opening-set bagel and saving two match points to upset the US Open champion 0-6 6-4 7-6 (10-8).
Sock can now look forward to taking on Simon, who claimed the scalp of third seed Wawrinka with a 6-4 6-4 victory in the final match of the day.
Defending champion Djokovic and second seed Murray were straight-sets winners over Vasek Pospisil and Lucas Pouille respectively.
Jo-Wilfried Tsonga, David Goffin, Roberto Bautista Agut and Mischa Zverev also advanced.
SIMON STUNS WAWRINKA
Simon last beat Wawrinka in this tournament two years ago and the Frenchman repeated that feat to end a run of 10 consecutive defeats against top-10 opponents.
US Open champion Wawrinka made an encouraging start to open up a 3-1 lead, but Simon responded with two breaks to take the first set and claimed another two in the second to send the world number three packing.
The unseeded Simon fended off five break points as Wawrinka endured further disappointment after suffering defeat to Alexander Zverev in the final of the St. Petersburg Open last month.
Simon reached the final after beating the Swiss in Shanghai two years ago and is just two victories from playing in another title decider in China.
SOCK ENDS DISMAL RAONIC RUN
Raonic had won his previous eight matches against Sock, but the world number 25 ended a three-year wait for a victory against the Wimbledon runner-up with a battling display.
Fifth seed Raonic would have returned to a career-high number four in the world if he had beaten Sock, but failed to build on a commanding start as he was bundled out in round two.
Sock was blown away in the first set, but rallied in style and fended off two match points in a final-set tie-break to claim an unexpected triumph.
DJOKOVIC AND MURRAY MARCH ON
Top seed Djokovic avoided drama in his contest with Pospisil, wrapping up a 6-4 6-4 victory.
The Serb bossed the baseline battles and left plenty in the tank as he eyes an eighth Tour-level win title of the year in his first tournament since losing the US Open final to Wawrinka.
Mischa Zverev will be the next opponent for Djokovic, while Murray takes on Goffin after the Wimbledon champion wasted no time in beating 13th seed Pouille 6-1 6-3.
Murray, striving to dislodge Djokovic at the top of the rankings by the end of the year, won the first five games of a one-sided match and never looked back as he won in an hour and 17 minutes.
MIXED FORTUNES FOR ZVEREV BROTHERS
Qualifier Mischa Zverev is through to his second ATP Masters 1000 quarter-final following a 6-7 (4-7) 6-4 6-1 success over Marcel Granollers.
His young brother Alexander had earlier lost his cool, smashing a racket during a 6-7 (4-7) 6-2 7-5 loss to ninth seed Tsonga.
Gael Monfils, eyeing a place in the ATP Finals, was beaten by Goffin, while Bautista Agut got the better of Viktor Troicki.