Rafa Nadal suffered his first claycourt defeat in 23 matches on Thursday and threatened to boycott next year's Madrid Open if officials did not ditch the blue clay that players have labelled "too slippery" and only fit for "smurfs (to) play on".
After the shock 6-3, 3-6, 7-5 third-round reverse to fellow Spaniard Fernando Verdasco, the French Open champion vowed not to return to the Masters event unless traditional red courts, which are slower and more suited to his game, were reinstated.
World No 1 Novak Djokovic has also been severely critical of the playing surface and after his 7-6, 6-4 victory against unseeded Swiss Stanislas Wawrinka said he too would shun the event next year unless the blue clay was discarded.
"The movements are very important for me and here I cannot move so I cannot hit the ball the way that I want," Nadal said after squandering a 5-2 lead in the final set against 15th seed Verdasco.
"The ATP and the tournament can do what they want," he added referring to the controversial innovation sanctioned by the governing body of men's tennis for this year's tournament.
"I tried my best to prepare but I wasn't good enough to adapt my game to this court.
"The only thing that I know is that if things continue like this I am very sad but next year will be one less tournament in my calendar."
Nadal's outburst was perhaps understandable considering he would have been confident of beating Verdasco having won all 13 of their previous meetings.
However, an error-strewn performance ended the Spaniard's bid for a third straight clay title this season and deprived him of a chance to avenge his defeat by Djokovic in last year's final.
He also faces the prospect of Roger Federer replacing him as World No 2 if the Swiss, the 2009 champion, wins the title on Sunday.
Djokovic looked equally uncomfortable sliding his way to victory over Wawrinka in the final match of the day on the Manolo Santana show court and the Serb will play his seventh-seeded compatriot Janko Tipsarevic for a place in Saturday's semi-finals.
Federer, who has also opposed the introduction of blue clay, cruised into the last eight with a 6-3, 6-2 win against French 14th seed Richard Gasquet and will meet fifth-seeded Spaniard David Ferrer on Friday.
The Swiss maestro had a tough time in the second round on Wednesday, edging out big-serving Canadian Milos Raonic, but had no such trouble against Gasquet as he chases a fourth title of the year.
"I played clean tennis even though I went for my shots," Federer said.
"Maybe I made a few too many unforced errors but that's due to the ball flying here and being tough to control," added the 30-year-old, who said he understood Nadal's frustration with the playing surface.
Verdasco's first win against Nadal was all the more astonishing given that the second seed twice failed to serve out the match in the deciding set.
Verdasco broke his Davis Cup team mate seven times in all, losing his own serve six times, and clubbed 31 winners to his opponent's 19.
A typically crashing forehand drive sealed victory on his second match point and he fell flat on his back on the court before kissing the clay and heading off to play a doubles match.
"Of course I am unbelievably happy and it's the biggest victory of my career," Verdasco said.
"It was unbelievable emotion and I will never forget it," he added. "It was a long time losing, many years, and finally I did it here in Madrid so you can imagine how happy I am."
Verdasco next plays Czech sixth seed Tomas Berdych, who was the first player into the last eight when he thrashed 12th-seeded Frenchman Gael Monfils 6-1, 6-1.
He was joined by Ukraine's Alexandr Dolgopolov, the 16th seed, who edged out French fourth seed Jo-Wilfried Tsonga 7-5, 3-6, 7-6 and Ferrer, who squeaked past countryman Nicolas Almagro 7-6, 3-6, 7-6.
Dolgopolov will play 10th seed and former US Open champion Juan Martin Del Potro after the rangy Argentine thumped fellow big-server Marin Cilic of Croatia 6-2, 6-4.Photograph: Mike Hewitt / Getty Images