Lleyton Hewitt battled through the pain barrier to win a second straight five-set epic and book his place in the semi-finals of the Australian Open.

Hewitt again needed on-court treatment for a hip injury as he scraped past Argentina's David Nalbandian in front of a capacity 16,000 crowd on Australia Day in Melbourne.

The third seed was three times within two points of defeat in the decider but eventually sealed a 6-3 6-2 1-6 3-6 10-8 victory in four hours five minutes, the fifth set taking an hour and 41 minutes.

It was a typical fighting display from the 23-year-old and not for the first time in the centenary championships there was obvious ill-feeling between the players.

Juan Ignacio Chela spat at Hewitt in their third-round match after tiring of his frequent cries of 'come on', especially after his own errors rather than Hewitt winners.

Nalbandian admitted before the game many players did not like the Australian's antics and he and Hewitt twice exchanged words at the change of ends, also bumping into each other as they crossed at the net.

''He is not a gentleman,'' said Nalbandian. What he does is not good for tennis. His attitude speaks for itself.''

On the incident Hewitt would only say: ''He brought it on himself a little. He sort of waited for a bit of a shoulder.''

Hewitt will now play Andy Roddick in the semi-finals, the second seed enjoying another easy day when Nikolay Davydenko retired with breathing problems in the third set.

Roddick, who was leading two sets to love and 4-1 at the time, has played just seven and a half hours compared with over 14 for Hewitt, but Hewitt is confident he will be fit for tomorrow's clash.

''He has an advantage because he's in bed already but come Friday night I'll be ready to go,'' said Hewitt.

''A year ago on this day I lost and thank Christ I came away with a win tonight.

''I just kept hanging in there, it was always tough serving second in the fifth set.

''I told myself to give everything and in the end it paid off once again. Yet again the never-say-die attitude came out.

''It's a long way from holding that trophy up there but I'm hanging in there. Only four guys left that can win and we're the top four in the world.

''It's set up for a pretty good showdown in the semis and finals.''

This was the first meeting between the pair since the 2002 Wimbledon final, which Hewitt won for the loss of just six games.

Earlier, Roddick's stroll through the championships continued when Davydenko indicated he was unable to continue in the stifling heat in Melbourne.

The Russian had received treatment on court during the second set, which he lost 7-5, and decided enough was enough after going two breaks down in the third set.

* Serena Williams was still taking her seat when the first question was asked - and what a question it was.

''The prevailing talk is that the Williams are declining. Venus has lost. Do you feel you need to win this tournament to counter that sort of talk?'' asked the man from the Boston Globe.

''I don't appreciate that language, to be honest with you,'' bristled Williams, who was preparing to face Maria Sharapova in the semi-finals of the Australian Open.

''We're not declining. I know that I'm one of the best players out here.''