Richard Williams says so much, runs his mouth so indiscriminately, you have to forget half of what he says and ignore the other half. But sometimes, usually when he's making an observation about his daughters, he can be downright prescient.

Years ago, back when Venus and Serena Williams were little girls playing on public courts in Compton, Calif., their father would tell visitors that Serena, the little one, would one day be better than Venus, the prodigy. We would roll our eyes and fix them back on Venus--taller, faster, infinitely more athletic. Venus was WOW! Serena was, well, somebody's little sister. And Richard would say knowingly, "You'll see."

I'm not sure why he said that back then, or why he has maintained it over the years, or even what purpose it served, exactly, to take such a position publicly. But there was a time, a few years ago, when the Williams family visited Lansdowne, the beautiful conference resort outside of Leesburg. Richard said it then, too, something about "stride-motion" or some such indicator being a good forecast of tennis talent. The girls were 13 and 11 that summer, at such an early stage of tennis evolution. There's a story making the rounds that he once said Venus had better win a Grand Slam before Serena grew up because it might be too late thereafter.

Friday afternoon, Serena made Dad look good and stole big sister's WOW! at the same time. Serena is the one who cracked the 115 mph aces. Serena is the one who ran deep into the corners to chase down impossible shots. Serena is the one who looked stronger and faster and more athletic. Serena Williams, 5 feet 9 with muscles and curves everywhere, makes Martina Navratilova--who revolutionized fitness in women's athletics--look like a waif. Serena, still 17, looked like the best player in the Williams family, and perhaps the best player in women's tennis as she reached Saturday's U.S. Open final.

Asked about her increasing popularity, and the notion that she has become the biggest curiosity on the women's tour, the outgoing Serena said, ". . . I don't blame them. Got to get a look at Serena." And when asked about stepping out of her older sister's shadow, Serena said, "I won three tournaments this summer on my own. . . . I think everyone marks us as the Williams Sisters now, instead of Venus and her little sister Serena."

We have no choice any more. Venus, having lost an exhausting and exacting semifinal match of her own to Martina Hingis, is gone. Serena is still here. And it's not like Serena got to the U.S. Open final by walking through some unseeded qualifiers. In the quarterfinals, she whipped Monica Seles, winner of nine Grand Slam titles. In Friday's semifinal, she held off Lindsay Davenport, the defending champion here, the Wimbledon champion two months ago, the No. 2 player in the world, in three sets. I don't know that any player in tennis the last 20 years gets more out of limited ability than Davenport, unless it's Todd Martin, who also seems to squeeze every drop of ability from his body year after year. Beating Davenport has become a terribly big deal.

Williams-Davenport wasn't one of the great artistic successes you'll ever see. But there were two masterful games, both won by Serena, that told the story of the match. In the third set, with Williams having broken Davenport's serve for a 4-3 lead, the two played an 11-minute game. Davenport had five break points, but couldn't pull even in the set's critical game. "Every break point I had, she served really well," Davenport said. "I never got a second serve. I never got a serve slower than 105 miles per hour." It took five game points, but Williams held for the 5-3 lead.

Then, there was the final game of the match. Williams hit a 115 mph service winner, followed two points later by another 115 mph service winner, followed by a 108 mph ace, followed by a 77 mph change-of-pace second serve that twisted, then kicked straight into the body of Davenport, who couldn't react quickly enough to return. Game, set, match. "She's had a great year," Davenport said. "I'm upset that I lost, but she just played a better match."

Finally, it was time for Big Sis. Asked if she wished her sister good luck as one took the court and the other headed triumphantly for the locker room, Serena said, "It's not a matter of luck. . . . I go sweat in the sun every day when I could be at the pool with some lemonade. That's not luck."

It doesn't take long to figure out which Williams sister is cockier: Serena, by a mile. Venus can be a little flip now and then, but is pretty diplomatic for the most part. Serena's a scream. She likes going for a line in conversation as well as on the court. It was high school graduate Serena, growing tired of all the junk Hingis was talking the other day, who said, "I guess it has a little bit to do with not having a formal education." When asked how she felt after beating Davenport, Serena said, "I'm not through yet."

And she's still here because her ability to think her way through a match is catching up with her surreal physical ability, which she uses to pound a tennis ball. "Physically," she said, "it's been there. It's innate with me. I didn't have to work too hard [on physique]. I have to work on the mental aspects."

And the utterly amazing thing is that the Williams sisters played so little junior tennis. As a result, Serena is learning how to concentrate at the pro level. Venus, 19, has been mentally tougher for a long time. But Venus was undone physically in her semifinal, cramps in her right leg conspiring to steal her biggest weapon. The player with the biggest serve in women's tennis (sometimes up to 120 mph) was weakly bouncing first serves into the bottom of the net by the middle of the third set.

Hingis-Venus was a grueling, prize fight of a match that left both women groping wearily for a second wind, for one more shot of adrenaline. In Hingis, Venus played a woman who might be smaller (6-2 to 5-8) but is just as fit, perhaps even quicker from sideline to sideline and easily the most arrogant woman on tour--maybe rightfully so.

But that might suit Serena just fine anyway. You see, Serena is 0-3 against Big Sister in professional matches. "She has a hard time playing her sister; maybe she should want Martina to win," Davenport had said of Serena's chances in the final.

Heaven only knows how good Serena will be when she tightens up her game, stops giving away loose points here and there, learns to think the points as well as she can play them physically. Somebody asked if she could envision herself holding the winner's trophy on Saturday afternoon, and she said, "I have to be more serious and consistent if I want to do that." With that as a priority, another championship-caliber player has officially arrived in women's tennis, and everybody is on notice, even family.

CAPTION: Venus Williams waves goodbye to her chance to win first Open title.