KEY BISCAYNE, Fla. (AP) - Steffi Graf extended her winning streak at the Lipton Championships to 21 consecutive matches by beating Natasha Zvereva 6-2, 6-4 in the fourth round today.

Graf has won three titles at Key Biscayne since her last Lipton loss in 1993. She improved to 20-1against Zvereva, who double-faulted on match point.

Also moving to the quarterfinals was Hingis, who ended 19-year-old qualifier Marlene Weingartner's surprising run with a 6-0, 6-2 victory.

On Monday, Pete Sampras coupled his victory and Carlos Moya's loss to reclaim the No. 1 ranking he relinquished last week. Next week will be Sampras' 263rd week on top, seven shy of Ivan Lendl's record set from 1983-99.

``There's a good chance I can do it,'' Sampras said. ``I'm going to play this game for a couple more years, at least.''

Moya became No. 1 last week, but the Spaniard's reign was brief. Sampras saw little reason to celebrate his return to the top, however.

``I said it once, I'll say it a thousand times: It doesn't matter so much what you're ranked this time of year,'' he said. ``It really comes down to December.''

Sampras deserves credit for candor, even if the comments hurt his sport. With the popularity of men's tennis sagging in the United States, he deflates any attempt to stir interest in a five-player race for No. 1.

That's too bad, because Monday's matches were filled with drama.

Sampras advanced to the quarterfinals by beating Albert Costa 6-4, 6-4. Hours earlier, the top-ranked Moya succumbed to fatigue, nerves and Sebastien Grosjean, 3-6, 6-4, 7-6 (11-9).

The results ensured Sampras' return to No. 1 when the new computer rankings are released Monday. It's the seventh time he has reclaimed the top spot.

Four other top-15 players also lost - No. 4 Alex Corretja, No. 12 Karol Kucera, No. 13 Greg Rusedski and No. 8 Marcelo Rios, the defending champion.

Corretja had a chance at No. 1 until he was eliminated by Thomas Enqvist 7-5, 6-3. Patrick Rafter and Yevgeny Kafelnikov, who also came to Key Biscayne with a shot at No. 1, lost in the first week of the tournament.

``Between the top five guys and the rest of the guys, there really is no difference,'' Sampras said. ``All these guys ranked 15 to 50 are hungry. They come out swinging away, and you're going to see a lot of upsets.''

Francisco Clavet edged unseeded Vince Spadea 7-5, 4-6, 6-4, leaving Sampras as the only American in the men's draw.

In women's third-round play, Venus Williams eliminated Fabiola Zuluaga 6-3, 6-4, and Serena Williams beat Magui Serna 6-1, 6-0. The victories moved the sisters closer to a showdown Sunday.

``I'm not thinking about the final right now,'' said Serena, who has won 13 consecutive matches. ``That's what caused a hindrance to me in the past - looking too far ahead.''

Jana Novotna, Mary Pierce and Anna Kournikova also won.

Sampras was unhappy about being scheduled to play Costa on the grandstand court, but as it turned out, his complaints were premature. Center court became available late in the afternoon, so officials moved the match there.

And Sampras looked right at home, dispatching the dangerous Costa in 80 minutes.

``Strange things can happen when you're out on the grandstand,'' Sampras said. ``Fortunately the matches went pretty quick on the stadium, so I was able to get out there.''

Maybe Sampras was right to worry, because Moya's loss came on the grandstand.

``I just want to say two things,'' Moya said. ``First, which ranking do I have to have to play on center court? And second, never mind, because we are in the United States, so everything can happen here.''