MELBOURNE - Russia's Ekaterina Makarova seized on a listless performance from Serena Williams to send the five-time champion crashing in a major shock at the Australian Open on Monday.

In hot conditions, the little-known world number 56 won 6-2, 6-3 to end Williams' 17-match winning streak at Melbourne Park and reach her first ever grand slam quarter-final.

Williams, a 13-time slam-winner, was expected to cruise past the 23-year-old Russian, who surprised seventh seed Vera Zvonareva in the third round.

But almost from the first point it was obvious that Williams was not her usual self as mistakes came thick and fast from her racquet, 37 in all.

The 30-year-old's movement was also below-par and she often didn't even attempt to chase down wide balls. In contrast, Makarova was going after everything and waiting for the almost inevitable mistakes.

Makarova broke Williams twice in the first set to win the opener in 31 minutes, but Williams seemed to get things back on track with an early break in the second, only to surrender it the next game.

Makarova held serve to level the set at 2-2, then broke again as a frustrated Williams served three double-faults, the last to concede the game.

If the Russian was feeling any nerves at leading one of the greatest players in women's tennis history, she wasn't showing them as she confidently moved to a 5-3 lead, before attacking Williams' serve and bringing up her first match point at 30-40.

Williams saved the first match point, then two others with big serves, but on the fourth the American sent a forehand wide and Makarova was through.

"It's an amazing feeling, it's unbelievable," she said immediately afterwards. "She's an unbelievable player and I'm just really happy."

The loss ended Williams' 17-match winning streak at Melbourne Park, which began at the 2009 Open. She won in 2009 and 2010 before missing last year with injury.

It was the American's first loss to a player outside the top 50 in three years, when she went down to world number 95 Klara Zakopalova in Marbella.

Meanwhile, Andy Murray took the easy route to the quarter-finals when Kazakhstan's Mikhail Kukushkin retired injured, as Wimbledon winner Petra Kvitova fought off a case of the yips.

Under blazing sun Murray, seeking Britain's first grand slam title since before World War II, was always in command and he led 6-1, 6-1, 1-0 when Kukushkin pulled out with a hip muscle injury on 49 minutes.

The truncated match ended an entertaining run by Kukushkin, inevitably dubbed "Borat" by the British press, who won an oddball encounter in the previous round to become Kazakhstan's best male grand slam performer.

"It's so hot on the court," said Murray, who will play Jo-Wilfried Tsonga or Kei Nishikori in the quarter-finals.

Kvitova reached the quarter-finals with a 6-2, 7-6 (7/2) win over Ana Ivanovic—but not before a temporary meltdown in which she embarrassingly swung and missed a simple overhead.

The cringe-making mistake late in the second set precipitated a brief nosedive and a flurry of errors but tough Kvitova steadied herself to seize control of the all-important tiebreak.