Ferrer stuns injured Nadal, Murray, Clijsters surge ahead

A tearful Rafa Nadal was stunned 6-4, 6-2, 6-3 by fellow Spaniard David Ferrer in the Australian Open quarter-finals on Wednesday, ending his quest to hold all four Grand Slam titles at once.

A leg injury suffered early in the match made the world number one's bid to become only the third man, and first since 1969, to achieve the feat almost impossible.

Nadal, the 2009 Melbourne champion, took an early medical timeout after tweaking his left hamstring, shaking his head as he trudged off Rod Laver Arena.

The nine-times Grand Slam champion returned with his thigh strapped but was clearly in pain, wincing and muttering to his uncle and coach Toni.

Seventh seed Ferrer, who had lost 11 of his previous 14 meetings with Nadal, including the last seven, showed no mercy, ripping shots to all corners to keep the pressure on.

A tortured Nadal slumped in his seat with his head in his hands after another thumping forehand down the line gave Ferrer a two-set lead.

Moments later, he was choking back tears after Ferrer tore into a 3-0 lead in the third but he battled like a true champion to get on the board, even forcing a break point at 4-2 down.

However, Ferrer kept his nerve and closed out the quarter-final with another big forehand after two hours and 33 minutes.

Nadal exited the year's first Grand Slam at the same stage and in the same manner in 2010, suffering a knee injury against Britain's Andy Murray.

Ferrer, who drilled 44 winners past his suffering compatriot, will face fifth seed Murray in only his second Grand Slam semi-final appearance.

Andy Murray ended Alexandr Dolgopolov's brilliant debut at Melbourne Park, slaying the giant-killing Ukrainian 7-5, 6-3, 6-7, 6-3 with an impeccable defensive game to ease into the semi-finals of the Australian Open on Wednesday.

Up two sets and a break in the third, the spring-heeled Scot appeared to be cruising to victory, but was stunned when Dolgopolov broke back and prevailed in a tense battle of nerves to win the tiebreaker 7-3.

The resurgence was to prove fleeting as Dolgopolov self-destructed early in the fourth set, falling back 4-0 to allow Murray to calmly serve out the 186-minute match on a chilly summer's day at Rod Laver Arena.

The victory ensured fifth seed Murray entered his second successive semi-final at Melbourne Park as he seeks to end Britain's 75-year wait for a men's Grand Slam champion.

The Briton will play David Ferrer for a place in the final.

Third seed Kim Clijsters survived a stern test of her Australian Open credentials by overcoming Poland's Agnieszka Radwanska 6-3, 7-6 to reach the semi-finals on Wednesday.

Clijsters, a Melbourne finalist in 2004, underlined her billing as tournament favourite but was forced to scrap by 12th seed Radwanska in unseasonably chilly conditions.

The Belgian, who won the third of her three US Open titles last year, traded breaks at the start with her Polish opponent before taking the first set in 29 minutes.

Radwanska forced a tiebreak in the second, but Clijsters quickly snuffed out the danger, sealing it 7-4 with a bullet of a backhand to set up a clash with second seed Vera Zvonareva.

Vera Zvonareva came a step closer to her maiden Grand Slam on Wednesday, muscling her way into the semi-finals of the Australian Open with a 6-2 6-4 win over rangy Czech Petra Kvitova.

The Russian bullied the 20-year-old's serve with a fierce display of clean hitting from the baseline then weathered a late fightback to close out the match in 75 minutes.

"She's (had) a great run here," Zvonareva said in a courtside interview of Kvitova, who knocked off seeds in her path to the quarter-finals but struggled to find her line against the Russian.

"I was just trying to hang in the there and fight for every point, just try to stay aggressive and that's about it."

The world number two mowed through the first set in 29 minutes and marched to a 3-0 lead in the second before Wimbledon semi-finalist Kvitova snapped out of her stupor under leaden skies at Rod Laver Arena.

The sound of booming cannons fired as part of celebrations for the country's national holiday on Wednesday challenged the players' concentration, while what appeared to be an elderly spectator collapsing held up play for a couple of minutes.

Kvitova seemed to recover quickest from the distractions, breaking Zvonareva at 3-3 after a fierce baseline battle that ended with the Russian poking a forehand into the net.

"It was a bit of a difficult moment there ... It was a little bit distracting," said Zvonareva, finalist at Wimbledon and the US Open last year.

However, the 26-year-old held her nerve to break straight back then benefited from a net cord deflection at 5-4 that stopped the ball dead on Kvitova's side.

Kvitova, serving to stay in the match, scrambled forward to keep the ball in play, but Zvonareva calmly lobbed her to bring up match point and pumped her fists in celebration when the tiring Czech clubbed a forehand long to surrender.

Zvonareva will play Kim Clijsters for a place in the final.