Helena Sukova, who halted Martina Navratilova's 74-match winning streak at the 1984 Australian Open, knocked the three-time champion out of the Grand Slam tournament again Tuesday night.

The big-serving Czech beat Navratilova 6-2, 3-6, 9-7 in a dramatic quarterfinal before a packed center-court crowd at the National Tennis Stadium."The last time I beat her here, I was just trying to win a set," Sukova said. "This time, I thought I had a chance to win."

Navratilova twice served for the match in the seesaw final set, but Sukova held her off with a series of sizzling backhand winners.

After Sukova saved two break points and held for an 8-7 lead, Navratilova appeared ready to even the match again, moving ahead 30-love with an ace. However, Sukova quickly gained a match point and watched a shaky Navratilova hand her the victory on a double fault.

"It was nerve-wracking out there," Sukova said. "I was trying very hard not to think about the score."

The victory was Sukova's second in a row against Navratilova, but only her fourth in their 25-match series.

Sukova, the fifth seed, served seven aces and had 21 winning returns off Navratilova's serve.

Sukova's semifinal opponent will be unseeded Belinda Cordwell of New Zealand, who beat Sweden's Catarina Lindqvist 6-2, 2-6, 6-1. The other semifinal pits defending champion Steffi Graf of West Germany against archrival Gabriela Sabatini of Argentina.

Graf, who hasn't lost a set in the tournament, breezed past eighth-seeded Claudia Kohde-Kilsch of West Germany 6-2, 6-3 in 55 minutes, while Sabatini rallied from 1-3 down in the final set to beat sixth-seeded Zina Garrison of the United States 6-4, 2-6, 6-4.

"It's going to be hard for anyone to beat me," said Graf, who is seeking her fifth straight Grand Slam title. "It's obvious. It's been like that for a year now."

Sabatini, who defeated Graf twice last year but trails their series 2-14, also sounded confident.

"I won't be afraid when I go out and play her," she said. "I don't feel any pressure. I think I have a good chance to beat her."

In men's play, longtime rivals Ivan Lendl and John McEnroe set up a quarterfinal showdown with straight-set victories.

Lendl recovered from a slow start to beat Israeli Amos Mansdorf 7-6 (7-2), 6-4, 6-2, while McEnroe cruised to a 7-6 (7-4), 6-2, 6-3 victory over fellow American Aaron Krickstein.

"I've come a long way," said McEnroe, who is trying to regain the form that made him the world's No. 1 player in the early 1980s. "I feel more comfortable mentally, and my game is coming together." Two-time champion Stefan Edberg is scheduled to play 11th-seeded Thomas Muster of Austria in another quarterfinal Wednesday. Edberg injured his back near the end of his 6-4, 6-0, 6-2 win over hometown hero Pat Cash and may not be able to play. "We don't really know what the problem is," said Edberg's coach, Tony Pickard.