SERENA WILLIAMS vowed to “work five times as hard to make sure I never lose again” after crashing out in the second round of the French Open.

The tournament had previously lost Australian Open champions Stan Wawrinka and Li Na but Williams’s 6-2 6-2 defeat by Spain’s Garbine Muguruza at Roland Garros was on another level.

The world No1 went into the tournament strong favourite to retain the title she won for the second time 12 months ago.

But within an hour of her sister Venus losing to Anna Schmiedlova, Serena trudged off the court a beaten woman. The pair had been expected to meet in the third round.

The result was surprising enough but the manner of it added to the shock. The 32-year-old had never previously won fewer than five games in any grand slam match.

Meanwhile, coupled with Li’s loss to Kristina Mladenovic on Tuesday, it is the first time in the Open era the top two seeds in the women’s tournament have lost before the third round at any grand slam.

Williams, who made 29 unforced errors and hit only eight winners, said: “I don’t think anything worked for me today. It was one of those days. You can’t be on every day, and, gosh, I hate to be off during a grand slam. It happens. It’s not the end of the world.

“I think she played really well and she played really smart. It’s great because I’m going to go home and work five times as hard to make sure I never lose again.”

In cold and windy conditions on court Suzanne Lenglen she simply never got going.

But she said: “It’s great sometimes to get knocked down because you have to get back up. I love getting back up. I love the challenge.”

But, as poor as Serena was, the match was just as much about the performance of 20-year-old world No35 Muguruza who struck the ball with great power and precision and was nerveless serving out the biggest win of her life.

Venus performed much better than her sister, racing through the first set but Schmiedlova showed impressive composure to turn the match around and win 2-6 6-3 6-4.