KEY BISCAYNE, Fla. (AP) - At the ripe old age of 18, Martina Hingis is now the wily veteran trying to hold off the cocksure youngster.

No longer the new kid on the block, Hingis finds herself in a different role against Serena Williams in Friday's semifinals at the Lipton Championships.

Hingis is ranked No. 1, but Williams, 17, is on a roll. Williams won her 15th consecutive match Wednesday, outslugging Amanda Coetzer 6-4, 6-0.

Hingis, who has lost just 11 games in four matches, advanced by beating Barbara Schett 6-1, 6-1.

``I haven't heard too much about Martina in this tournament,'' Williams said. ``We haven't played in a little while. It should be a good match.''

Williams is 0-2 against Hingis, but has become a much better player since their most recent meeting at Los Angeles in August.

``I have some business to take care of,'' Williams said. ``When I last played her, I couldn't play. I'm sure you can decipher the difference.''

The two teens also met in the quarterfinals at Lipton a year ago, when Williams squandered two match points before Hingis prevailed in a third-set tiebreaker.

``I had two match points last year?'' Williams said facetiously. ``It must really not be on my mind.''

Williams and Hingis could serve as poster children for the new wave of confident kids dominating the WTA Tour spotlight.

But there's almost a generation gap between them because Hingis has won five Grand Slams and been ranked No. 1 for 85 weeks, while Williams won the first two tournament titles of her career in the past month.

Hingis said she's excited about facing Williams.

``The last time I played her was quite a while ago,'' Hingis said. ``She's definitely a more experienced player now.''

In the men's quarterfinals Wednesday, Francisco Clavet eliminated Nicolas Kiefer 7-5, 6-3, and Sebastien Grosjean won a battle of unseeded players by beating Dominik Hrbaty 6-3, 5-7, 6-1. For the first time in the Lipton's 15-year history, there will be no Americans in the men's semifinals.

The last two women's quarterfinals today pitted second-ranked Lindsay Davenport against No. 7 Steffi Graf, and No. 4 Jana Novotna against No. 6 Venus Williams, the defending champion.

``Nobody can say who is going to win this tournament,'' Schett said.

Don't discount Hingis. The Swiss miss is no longer the freshest face on the WTA Tour, with teen-agers Amelie Mauresmo and the Williams sisters among those challenging her reign. But Hingis leads all players with 21 victories this year and beat Mauresmo in the final of the Australian Open.

Last year Hingis lost in the semifinals of the French Open, Wimbledon and the U.S. Open, then lost the No. 1 ranking to Davenport. Chastened, she prepared for 1999 by training with Nick Bollettieri in Bradenton, Fla.

``That was the first time after a long time that I really worked for two weeks, day after day, three or four hours of tennis,'' she said. ``I lost some weight, and that was like the best thing I could do. You stop growing, and you start growing to the side.''

Fit and trim again, Hingis has regained her remarkable sense of anticipation. Her serve and forehand, meanwhile, are more powerful than before.

``You can see it,'' she said. ``I mean, I'm back to No. 1. The scores tell it.''