Sports : Navratilova Upset in Melbourne

In the biggest upset of the $4-million Australian Open tennis women’s championships, fifth-seeded Helena Sukova of Czechoslovakia defeated three-time champion Martina Navratilova 6-2, 3-6, 9-7 today to gain the semifinals.

A frustrated Navratilova, who had hoped to regain her once indomitable form, said Sukova’s aggression had made the difference.

‘She hits winners all over the place when she plays me because there is no pressure on her,” Navratilova said. “I had my chances, but she came up with the big shots.”

Defending champion Steffi Graf of West Germany moved into semifinals of the women’s singles with a 6-2, 6-3 triumph over compatriot Claudia Kohde-Kilsch. (Story in Sports Section.)

Oozing confidence after her victory, Graf said “It’s going to be hard for anyone to beat me. It’s obvious. It’s been like that for a year now.”

Also advancing to the semifinals among the women were No. 3 Gabriela Sabatini of Argentina and unseeded New Zealander Belinda Cordwell.