Slobodan Zivojinovic of Yugoslavia got a little help from a friend before he defeated second-seeded John McEnroe on Wednesday in the quarterfinals of the Australian Open tennis championships.

The unseeded Zivojinovic, 22, 66th in the world rankings, beat McEnroe, 2-6, 6-3, 1-6, 6-4, 6-0.

Zivojinovic, who is the doubles partner of Wimbledon champion Boris Becker, said practicing with Becker had helped him prepare.

"I have to say thank you to Boris. When you play with someone who is fast, you start to play better and better," he said.

McEnroe has not won a Grand Slam title this year and has no hope of overtaking Ivan Lendl for the world's No. 1 ranking. Top-seeded Lendl defeated Britain's John Lloyd, 7-6, 6-2, 6-1, today to advance to the semifinals.

McEnroe's serve and delicate touch held no mysteries for Zivojinovic, who powered his way to victory. He served immaculately in the final two sets and treated McEnroe's own serve with disdain, defusing it regularly with strong returns.

In the fifth game of the final set, McEnroe shouted to Zivojinovic: "You are going to pay for this. I mean it."

McEnroe raised the ire of the capacity crowd of 10,000 by storming angrily from the court after his defeat. He jumped into a waiting car with his actress girlfriend, Tatum O'Neal, and made a hasty exit. McEnroe, who already had been fined $2,750 on two charges of abuse during the Open, was fined $1,000 for refusing to attend a compulsory news conference.

Zivojinovic defeated reigning Australian Open champion Mats Wilander in the first round at Wimbledon. In the semifinals Friday, he will meet Wilander, who beat sixth-seeded Johan Kriek, 6-3, 7-5, 6-2.

Zivojinovic had not reached a Grand Slam semifinal previously. Last year he earned only $17,601 from tennis. He will earn $24,903 just for making the semifinals here.

Zivojinovic won the support of most of the crowd in the fourth set, when McEnroe was involved in a dispute with the umpire and called for referee Peter Bellenger. Zivojinovic joined some spectators and had a sandwich. "You know how McEnroe is," he said. "I just sat down."

Chris Evert Lloyd scored a disputed 6-1, 7-6 victory over fifth-seeded Claudia Kohde-Kilsch to advance to the women's singles final.

Evert appeared to lose the second-set tie breaker when she hit a ball that seemed to go long, but the ball was called good.

Evert will play Martina Navratilova, who beat third-seeded Hana Mandlikova, 6-7, 6-1, 6-4.