Seeded third, but favourite for the title, Agassi withdrew without waiting to see if a further 24 hours’ rest brought any significant difference.

He was not due to play until tomorrow, but made his decision late on Sunday night.

Agassi started feeling pain as he lost the final of the Commonwealth Bank International at nearby Kooyong to Pete Sampras on Saturday.

‘‘It started early in the match against Pete and gradually got worse,’’ said Agassi, his hopes of becoming the first person since Roy Emerson in 1965 to win three Australian Opens in a row crushed.

‘‘Waking up this morning I didn’t feel any better, but even if I had I would have felt in a difficult position. In a best case scenario I would be playing with a pretty significant concern and fear in my mind.

‘‘So really the decision was not an easy one, but a pretty clear one.

‘‘I’m disappointed at not playing because I’ve done well here and it’s a big step backwards as far as my year is concerned.

‘‘I have to get back (to America) and get to the bottom of it. I can only go on my experience in the past, which is not a good one.

‘‘It was an attempt to play through some pain back in ’93 that lead to eventual surgery.

‘‘When they did it they suggested that it was wear and tear with haemorrhaging and tissue and they would clean that out, but there was no guarantee how long that would last. So there is a long-term concern there. It’s a difficult situation.

‘‘I’ve probably gotten a lot more use out of it than I would ever have guessed, but hopefully it is something that by treating it immediately I can get through.

‘‘But I’m always worried (about the long-term effect). It’s certainly not something I want to linger very long. Surgery is always a last resort. I don’t think I’m there yet.

‘‘But we’ll have to see I don’t know. The first thing is to get it clearly assessed and make sure we know what it is. Last time we didn’t know what it was until we got in there.

‘‘I’ve had nothing since then that has startled me to this degree.

‘‘When you can’t stretch your wrist back or get in what I would call a push-up position, the last thing you can do is stop a 130-mile-an-hour shot and redirect it with any sort of pace at all.

‘‘The trauma that your body goes through on the tennis court far outweighs anything you could experience in everyday life, so if you feel it there it is pretty clear.

‘‘There is no greater investment than your body when it comes to professional athletics, so I need to make sure I’m OK.’’

The championship lost another of its stars without them hitting a shot when women’s fifth seed Serena Williams failed to recover from the ankle problem she suffered in Sydney last week.

And France’s Mary Pierce lasted only 18 minutes against American Jill Craybas before quitting with shoulder trouble.

Williams had been seeded to meet her sister Venus, favourite to add the crown to her Wimbledon and US Open triumphs, in the semi-finals.

‘‘It’s very disappointing, especially coming all this way and having to turn around and go back home,’’ said Williams.

‘‘I said a lot of prayers, but when I went to practise yesterday I couldn’t really move on my toes.

‘‘I didn’t want to have a possibility of wasting three months. Hopefully taking this off I can come back a little sooner.

‘‘This is just a small hiccup in the road - a small pebble I’m going to jump over.’’

She had asked tournament officials for a delay to her match with former Wimbledon champion Conchita Martinez, but it was not granted.

‘‘I’m not in here to start a controversy or anything. I’m just here to take it as a champion. Things don’t always go your way in life.’’