Stich Uses Power; Novacek Hangs On : U.S. Open: They win with different styles and will play each other in semifinals.

Two players as different as night and day, which is when they played Thursday in the U.S. Open tennis tournament, advanced to the men’s singles semifinals. They were Michael Stich of Germany and Karel Novacek of the Czech Republic, the Mutt and Jeff of the men’s semifinal survivors.

Stich, seeded fourth, served and volleyed his way past a dangerous Jonas Bjorkman of Sweden in an evening session on Stadium Court that had the packed house of about 20,000 rooting and raucous. The final score was 6-4, 6-4, 6-7 (9-7), 6-4, and the athleticism and risk-taking demonstrated by Stich and Bjorkman had the place rocking.

Novacek stayed on the baseline and outlasted Jaime Yzaga of Peru, the previous-round conqueror of top-seeded Pete Sampras, in an afternoon session on Stadium Court that attracted a few thousand fewer than the night session and drove a few thousand more to the concession stands in boredom. The final score was 6-2, 6-7 (9-7), 6-1, 5-7, 6-3, and the biggest risk taken by Novacek and Yzaga was switching rackets at the changeover.

Stich served mostly bullets, and Novacek, who had six set points in the second set and still was stretched to five sets by the always-game Yzaga, mostly dodged them.

Their victories completed a semifinal field that had closed out the lower half of the bracket Wednesday night with victories by Andre Agassi and Todd Martin. While that matchup promises to be intriguing, so could Stich-Novacek because of the greatly varying style of their play.

“I am happy to be in the semifinals,” Stich said, “but I have been at this level before and I know full well that there are two matches left to get to where I want to get. Saturday, I must play better.”

Saturday, he must expect an opponent rooted to the baseline. Which is where Novacek feels most comfortable and from where he has taken himself to his furthest-ever Grand Slam tournament advancement. He has been a top 10 player in the past, and despite being only six months shy of his 30th birthday and having slipped all the way to No. 56 in the rankings, he has persevered in the Grand Slam event where that counts the most. Before this, he is perhaps best remembered in this country as the seeded player who was routed by Jimmy Connors in 1991 during Connors’ sensational run to the U.S. Open semifinals.

Stich, of course, is best remembered for winning the 1991 Wimbledon title. After that, he suddenly became the tall, hard-serving German who wasn’t Boris Becker.

Now, Stich, No. 4 in the world, has come through the draw here as the highest ranked and seeded man. And while he had his tough moments against a good new talent in Bjorkman, losing his first set of the tournament, he generally played the kind of quality match that can be competitive for the title here.

While struggling with his serve, he still got to the net 126 times and won points on 63% of those approaches. Bjorkman came in 116 times and won points on 62% of those charges. Twice in the match, including once in the third-set tiebreaker, Bjorkman took 123 m.p.h. Stich serves, cranked them back almost as fast as they had come, rushed the net and won the point.

“He was unbelievable,” Stich said of Bjorkman, who lives in the same city in Sweden that Stefan Edberg does, plays the same type of game that Edberg does, with an Edberg-endorsed Wilson racket, and knocked Edberg out of the tournament earlier this week.

Novacek admitted afterward that the match, in which he and Yzaga totaled 151 unforced errors--Novacek having 78--had negative elements.

“I was nervous during the second set, and I lost my concentration,” he said. “I choked on a couple of points.”

He also hit 27 aces, but on the big serves that Yzaga did get back, Novacek stayed on the baseline, exchanging ground strokes.

Open Notes

Pat Galbraith, former UCLA doubles All-American and Pacific 10 singles champion, teamed with Elna Reinach of South Africa to win the mixed doubles title, beating top-seeded Todd Woodbridge of Australia and Jana Novotna of the Czech Republic, 6-2, 6-4. It was Galbraith’s first Grand Slam doubles title after two second-place finishes the last two years at Wimbledon, with Grant Connell of Canada. . . . Meilen Tu of Northridge, seeded No. 4 in the Junior Girls singles here, advanced to the quarterfinals by beating Nannie de Villiers of South Africa, No. 16. The score was 6-1, 7-5.