The difference today between Martina Navratilova and Hana Mandlikova, the two best semifinalists in the $500,000 Virginia Slims Championships, was as narrow as a broken string on a tennis racket.

Mandlikova's racket string broke on the point that could have won her the second set from Navratilova this afternoon in front of 15,786 at Madison Square Garden, the largest crowd to ever watch a women's tournament match.

Mandlikova's will finally broke two points later.

Navratilova, the top seed, defeated No. 3 Mandlikova, 7-5, 7-6 (9-7), in what she said was the best match the two native Czechoslovakians have ever played.

As the natives would say here, it's all ova.

In Sunday's final, Navratilova will play Helena Sukova, the 20-year-old Czechoslovakian who upset her at the Australian Open last December to end a 74-match winning streak.

Sukova, the fifth seed, defeated unseeded Kathy Rinaldi, 6-4, 6-2, in today's earlier match.

Navratilova, the defending champion, survived set point in each set, as well as four service breaks.

"It was just a lottery ticket out there," she said later, smiling.

If the first set was heart-breaking for Mandlikova, the second was just plain old bad luck. They traded games all the way to the 12-point tie breaker (which must be won by two points). Navratilova had the first advantage, 6-5, but she hit a backhand volley long, and Mandlikova drew even.

Mandlikova won the next point on a cross-court forehand, passing Navratilova at the net for a 7-6 lead.

It then was her chance to win the set, but what happened next had to warm the hearts of hackers everywhere.

Mandlikova lunged for Navratilova's serve to her backhand and, to her horror, hit a stray pop up into the far stands. A string had picked the worst of times to snap.

"It's set point for her, and I get lucky," Navratilova said. "The ball takes off like it was on a trampoline."

At 7-7, Mandlikova, with a new racket, sent her backhand service return long. At 8-7, she drove Navratilova's cross-court forehand into the net, and, with it, perhaps Navratilova's strongest challenge of this tournament was over.

"When you win in two sets when she had set point in both sets, you're lucky," Navratilova said.

"Just a couple points," Mandlikova lamented. "Just two or three points made the difference.

"She was luckier today, not better. Luckier."

"If I were lucky," Navratilova countered, "then I'm glad . . . It was as close as you can get without going to three sets."

During one stretch of the first set, there were four consecutive service breaks, the last ending with Mandlikova holding a 5-4 lead. That last break, Mandlikova said later, "was very, very important."

She had a 5-3 lead and was serving. At 30 love, she couldn't handle Navratilova's overhead with a volley near the net. 30-15. Then, she double-faulted. Now at 30-30, she mishandled a volley at the net, and then lost the game on Navratilova's forehand smash.

"I missed a couple easy volleys," Mandlikova said. "It was a very, very good match. Every point was tough, every point was very, very good."

In the other match, Sukova, who is 6 feet 1 1/2, served nine aces, although Rinaldi thought her last one -- match point -- was wide. If it's any consolation, Sukova thought so, too.

"I thought it was wide, but I didn't really know what to do," Sukova said. "I didn't really think it made a difference . . . I was up, 5-2. It was just one point; it was bad luck that it was the last point."

Rinaldi, who is 5 feet 5 1/2, attempted to outmuscle Sukova from her usual spot on the base line. Sukova had other ideas. Several times, she brought Rinaldi dashing to the net with drop shots.

"She kept me off-balance throughout the whole match," Rinaldi said.

Yet Rinaldi had her chances. She broke Sukova's serve for 4-4 in the first set, but then was broken right back, losing the game on an overhead smash that fell out. Sukova then held serve for the set.

Sukova broke Rinaldi again in the third game of the second set for a 2-1 lead, then fought back from 15-40 with two consecutive aces to win the next game and ease through the second set.

If the all-Czech final brings back unpleasant memories for Navratilova of the loss in Australia, she certainly didn't show it.

When asked about Sukova, Navratilova, who is 5 feet 7 1/2, said, "I just hope she doesn't grow any more. She's tall enough, God knows."