Serena enters Australian Open semi-finals with comeback victory over Azarenka

Defending Australian Open champion Serena Williams staged a magnificent comeback to beat Belorussian Victoria Azarenka in a quarterfinal match on Wednesday. The American was in serious trouble at a set and 4-0 down in the second, but stormed back to win 4-6 7-6 (7-4) 6-2.

However, her sister Venus lost 2-6 7-6 (7-4) 7-5 to 16th seed Chinese Li Na.

At 4-0 down in the second set, Serena admitted: "I was actually thinking 'If I lose today and I lose in doubles I think I can catch a flight on Friday'. That's not what a champion is supposed to think, but that's what I was thinking.

"I'm just happy to still be here. I think I played good tennis today," said Azarenka, who also led Serena by one set last year before retiring with illness.

"It was very high level of tennis from both of us. I knew she would fight until the last point and she started playing unbelievable, I think, from 4-0. I mean, she was really in the zone at that point,” she added.