Serena Williams beats Victoria Azarenka at Wimbledon to stay on course for Grand Slam

Serena WIlliams came from a set down to reach the last four of Wimbledon with a 3-6 6-2 6-3 defeat of Victoria Azarenka.

The top seed maintained her 100 per cent record over Azarenka in Grand Slams and is still on course to win all four major titles in 2015.

Maria Sharapova is the most immediate obstacle in her path, and the Russian's CV does include a Wimbledon win over Williams, but that came back in the 2004 final.

Williams has won all but one of their 17 subsequent meetings, and the five-time champion is now a huge favourite to make it 21 Grand Slams and move to within one of Steffi Graf's open-era record.

Thoughts of lifting a sixth trophy were far from Serena's mind as she toiled in the opening set, surrendering a break to fall 4-1 behind.

Azarenka had never beaten the American at a major tournament, but was halfway to achieving this aim when she served out for a 1-0 lead.

Williams readied herself for another rearguard action and snatched her first break in the second set for a 4-2 lead

Pounding down a succession of aces, Serena protected her own serve and then broke the outgunned Azarenka for a second time to level the match.

The world No 1 took a big stride toward the semis when she breached the Belarusian's serve again early in the third.

But Azarenka grimly clung on, with both players exchanging passionate outbursts, and briefly brought up a break point of her own while Williams served for the match.

Answering with an ace, Serena quickly swatted away the danger and secured another meeting with Sharapova.

"It's been up and down. But somehow I'm still alive. I don't know how," said Williams, who lost to the teenage Sharapova in the 2004 Wimbledon final.

"Maria's been playing really well. I saw her match today. She's such a fighter and it's always good to see her doing well.

"We haven't played each other at Wimbledon in a while but I look forward to it. I just really don't have anything to lose."