By Greg Stutchbury

MELBOURNE (Reuters) - The spotlight may focused on the return of Belgian duo Justine Henin and Kim Clijsters, but Serena Williams proved again Wednesday she was the ultimate comeback queen.

A set down and trailing 4-0 in the second set to seventh seed Victoria Azarenka, the defending champion looked to be following older sister Venus out of the Australian Open quarter-finals.

The world number one rediscovered her game, however, to win the next five games and force a tiebreak before she blew the Belarussian off the court in the third to record a 4-6 7-6 6-2 victory.

"I wasn't playing my best, especially in the first two sets," Williams told reporters. "I definitely think I played well in the third. But, you know, I was down the whole match from the first point until the end.

"I thought she was aggressive the whole time. She's the kind of player you really have to take it to. I thought she played excellent."

William has made a habit of making sensational comebacks at the Australian Open. In 2003 she came back from 5-1 in the third set and then saved two match points to beat Clijsters in the semi-final. She then beat Venus in the final.

In 2005 at Melbourne Park, she saved three match points in the semi-final against Maria Sharapova before she beat Lindsay Davenport in the final.

Williams also saved a match point against Elena Dementieva in their Wimbledon semi-final last year.

The American said Wednesday's comeback was good but not as important.

"I can't say it's number one (in terms of importance) because I've been down match point several times," Williams said. "I know in '03 I was down some match points. It's nothing like being down match points." Azarenka paid tribute to Williams.

"I know she's gonna fight until the last point (and) she started playing unbelievable from four-love," she said. "She really really went for her shots, and she made them.

"The only thing I did is I probably backed up a little bit. I gave her more time to go for her shots. I mean, she was really in the zone at that point.

Azarenka added: "She knows how to handle herself, more experience, and I just have to learn from it."

(Editing by Alastair Himmer)