One day after reclaiming the No. 1 ranking, Pete Sampras lost Tuesday to nemesis Richard Krajicek in the quarterfinals of the Lipton Championships, 6-2, 7-6 (8-6).
Krajicek, the last player to beat Sampras at Wimbledon, has won their past four meetings.
Sampras regained the No. 1 ranking he relinquished last week by winning Monday while Carlos Moya lost. Despite Sampras' loss to Krajicek, next week will be his 263rd week on top -- seven shy of Ivan Lendl's record.
But Sampras continues to struggle following a lengthy layoff this winter. He is 7-3 this year and hasn't reached a final in his four tournaments.
The two-time Lipton champion was the last American in the men's draw.
Meanwhile, Steffi Graf extended her winning streak at Lipton to 21 consecutive matches by beating Natasha Zvereva 6-2, 6-4 in the fourth round Tuesday.
Graf has won three titles on Key Biscaynce since her last Lipton loss in 1993. She improved to 20-1 against Zvereva, who double-faulted on match point.
Also moving to the quarterfinals was Martina Hingis, who ended 19-year-old qualifier Marlene Weingartner's surprising run with a 6-0, 6-2 victory.
Sampras advanced Monday 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 lost Monday -- 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.
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.
"Strangthings 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."
©1999 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed