Seven-time grand slam-winner Venus Williams crashed out of the Madrid Open as men's top seed Novak Djokovic slammed tennis chiefs for not consulting players over a controversial new blue surface.
American wildcard Williams, 31, who is struggling to resurrect her career after a long injury and illness lay-off, went down 6-4, 6-1 to German 12th seed Angelique Kerber in round two.
This year, auto-immune disease-sufferer Williams has pulled out of both the Australian Open and the Malaysian Open, before reaching the quarter-finals in Miami and Charleston.
But her sister Serena Williams went through 6-3, 6-1 in her opening match against Russia's Elena Vesnina, despite the "early" start time of 11:00 am. "I always hate the early starts," she said.
Reigning women's champion Petra Kvitova kick-started her title defence with a 6-2, 6-3 defeat of New Zealand's Marina Erakovic.
The third-seeded Wimbledon title-holder, who defeated Victoria Azarenka in straight sets to lift the 2011 trophy, made it into the second round in 67 minutes, firing five aces and producing 28 winners.
There was also smooth progress for China's Li Na, who beat Spanish hope Silvia Soler-Espinosa 6-3, 6-1, while US Open champion Samantha Stosur came from a set down to beat Christina McHale 2-6, 6-4, 6-0 in the second round.
Meanwhile world number one and men's defending champion Djokovic fired a barb at tour chiefs over Madrid's experimental blue surface, and added that "all players" hoped it would not cause injuries.
"The hope of all players is that we won't have injuries and have a decent week of tennis," said the Monte Carlo Masters finalist, who skipped the ATP event in Belgrade last week after the death of his grandfather.
Djokovic joined with Spain's Rafael Nadal in criticising ATP chiefs for a lack of consultation. The ATP has had stormy relations with players in recent months and has faced strike calls over their share of grand slam profits.
"The only disappointing thing from a player standpoint is that it was decided without players agreeing to it," said the Serb. "Players should be agreeing to the change -- there should be some value in what they say.
"I'm not blaming the tournament, it is fighting for its own interests. But the ATP should have done a better job on player rights in protecting what the players want."
The proposal from larger-than-life billionaire Madrid impresario Ion Tiriac is on a one-year trial, with the event saying its purpose is to help spectators see the yellow ball more clearly on the blue surface.
"The blue clay surface makes this year different," Djokovic said. "It is the first time in history. It will be interesting for everyone to see what happens.
"There is a certain difference compared to red clay, but we have it (blue) in front of us. I tried to prepare for it as well as I could. But it's the same for everyone."
In men's play, Russian Mikhail Youzhny defeated local wild card Javier Marti 6-3, 6-2 and Serb Viktor Troicki beat American Donald Young 6-1, 4-6, 6-1.
Former French Open champion Juan Carlos Ferrero, 32, went down to Russian qualifier Igor Andreev, while Ferrero's fellow Spaniard Guillermo Garcia-Lopez ousted Marcos Baghdatis.