World number one Novak Djokovic was pushed to the limit before reaching the third round of the Madrid Open with a three-set win over Spanish qualifier Daniel Gimeno-Traver.
The world number 137 shocked the Serbian by breaking him twice to level the match in a stunning second set, but Djokovic recovered with the crucial final-set break to win 6-2 2-6 6-3 in one hour and 46 minutes.
And Djokovic was withering in his assessment of the blue clay surface for the tournament.
He said: "It's impossible to move. I hit maybe five balls, the rest went just trying to put the ball into the court. I was relying on serve and getting free points from his unforced errors.
"That was not tennis, either I need football shoes or some advice on how to play on this court. I cannot find the words to describe this court. It's really tough to play like this on a centre court.
"We cannot change anything this year, but my first impressions are not good. I don't want to be the one complaining, but I say honestly what I feel.
"We need serious discussion about the future of this blue clay."
In the day's other men's second-round match, sixth seed Tomas Berdych also advanced as he held off big-serving South African Kevin Anderson for a 6-4 6-3 success.
In the first round, 13th seed Feliciano Lopez was the only seeded casualty as he fell 3-6 7-6 (8/6) 6-4 to Austria's Jurgen Melzer, while recent Bucharest winner Gilles Simon was pushed in a 6-7 (7/1) 6-3 6-3 win over Italy's Fabio Fognini.
Other seeds to advance were 14th seed Richard Gasquet, who needed a final-set tie-break to see off Brazil's Thomaz Bellucci 4-6 6-4 7-6 (7/5), Juan Martin Del Potro, Alexandr Dolgopolov, Gael Monfils and Fernando Verdasco.
Veteran Czech Radek Stepanek surprised Australian youngster Bernard Tomic 6-2 7-5 and there were also wins for Marin Cilic, Milos Raonic, Andreas Seppi, Marcel Granollers, Federico Delbonis and Stanislas Wawrinka.