Wozniacki beats heat and Sharapova at US Open

Caroline Wozniacki showed she is back as a force in women's tennis by stunning Maria Sharapova to reach the quarter-finals of the US Open.

The popular Dane produced a display of real quality to win 6-4 2-6 6-2 and make the last eight at a grand slam for the first time since the Australian Open in 2012. The last time the Dane beat the Russian was at Flushing Meadows at the same stage four years ago, when she was in her pomp.

Wozniacki has been in fine form and was the better player in the opening set, but it was no surprise to see Sharapova hit back in the second.

Because of the hot and sticky conditions, the heat rule was in effect, meaning a 10-minute break between the second and third sets.

Sharapova took too long, though, and was given a time violation, while Wozniacki then complained to the umpire about the time her opponent was taking between serves. Wozniacki made the breakthrough in spectacular fashion in the fourth game.

In the quarter-finals, Wozniacki will play 13th seed Sara Errani, who ended the emotional run of qualifier Mirjana Lucic-Baroni. The Croatian was back in the fourth round at a slam for the first time since reaching the Wimbledon semi-finals aged 17 in 1999. Family and financial problems derailed her career but she is finally back on the big stage.

The statistics told the story of a match between two very different players, with Lucic-Baroni hitting 46 winners compared to just four for Errani. But ultimately the Italian’s tally of nine unforced errors and Lucic-Baroni’s mark of 69 proved the difference in Errani’s 6-3 2-6 6-0 victory.

Frenchman Gilles Simon delivered the first big surprise in the men’s draw, taking down fourth seed David Ferrer of Spain 6-3 3-6 6-1 6-3 to move into the fourth round.

With the loss Ferrer earned the dubious distinction of becoming the first top 10 men’s seed to be shown the exit while Simon moves on to face either big serving Croatian Marin Cilic or South African Kevin Anderson who clashed later in the day.

Today Jo-Wilfried Tsonga will go into his fourth-round match against Andy Murray boosted by the Briton's uncertain form. Murray has not won a title or beaten a top-10 player since Wimbledon in 2013.

Tsonga, one of the game’s thunderstorms, raging and fading unpredictably, has a 2-9 record against the Scot, but ended a six-year losing run in Toronto earlier this month.

“The locker room is maybe a bit less afraid of Andy because he’s losing a few more matches than in the past,” he said. “But I don’t know any player who once on court is going to be super confident against Andy. “He’s different than in the past maybe because I feel he’s not serving as strong as he used to, nor maybe hitting as strong as he used to.”

Murray’s response: “I’ve beaten many top 10 players over the course of my career in these events and I’m sure it will happen again, and happen soon. I’m sure that’s the case on Monday.”

Whoever wins, that side of the draw is going to take notice. Djokovic – who has been in blinding form in the first three rounds and should beat Philipp Kohlschreiber after the German’s grinding four-setter against John Isner – will not know what to expect in the quarters, so unpredictable have Murray and Tsonga been in recent weeks. - Reuters with additional reporting from Guardian service