Seles, 24, has pulled out of the year's first Grand Slam event - a tournament she has won four times - because of "personal reasons", but McNamee could not confirm whether her absence is connected to the health of her father and coach, Karoli, who has been suffering from stomach cancer.
"I don't want to speculate," McNamee said. "But I am disappointed that Monica won't be playing. She's a four-time former champion and a great friend of the tournament and Australia. She's never lost a singles match in Australia."
Seles' absence means she joins Steffi Graf in missing the tournament, which starts in Melbourne on 19 January. Mary Joe Fernandez, a former runner-up, has also ruled herself out.
The men's competition will also be missing a key player after Yevgeny Kafelnikov withdrew with a knee injury. The Russian will miss the tournament for the second successive year.
Andre Agassi progressed with ease in the traditional warm-up event for Melbourne, beating Jan Siemerink, 6-4, 6-3 in the Australian men's hardcourt championships yesterday.
Agassi, who struggled for form and fitness in 1997 as his ranking plummeted to 140 late in the year, said he was pleased with his performance. "The match needed me to be sharp early in the point and I was," he said. "I honestly feel every time I'm on the court it's a success to get through the match."
New Zealand's Brett Steven earned a third-round meeting with Agassi after beating the No 2 seed and French Open champion, Gustavo Kuerten, 6-3, 6-3.
Another seed, Sweden's Magnus Norman, was forced to retire from his match against Jerome Golmard after twisting his ankle in the third set. As a precaution, he was taken to hospital for X-rays.