the $6.44 million NASDAQ 100 Open on Sunday.
Jennifer Capriati, the top seed in the women's event, won, working her way through a dangerous third-round contest.
Adrian Voinea of Romania upset No. 2 Ferrero, 7-6 (8-6), 1-6, 6-2, and recorded the biggest upset so far at the second Tennis Masters Series event of the 2002 ATP Tour.
Former Miami champion and 32nd seed Marcelo Rios of Chile eliminated the third-seeded Kafelnikov, 6-4, 7-6 (7-4).
On the women's side, Capriati overcame 10 double faults and rallied past No. 32 Anastasia Myskina of Russia, 3-6, 7-5, 6-2.
Voinea posted his first victory over a top-10 player since 1996, when he triumphed over former world No. 1 Thomas Muster at Indian Wells.
Voinea halted his 13-game losing streak against top-10 players, improving to 3-21 against the best players on the ATP Tour.
Voinea next takes on Ecuador's Nicolas Lapentti. The 20th seed, Lapentti edged Czech Jiri Novak, the 13th seed, 7-6 (9-7), 7-6 (7-4).
Rios, who has captured five Tennis Masters Series titles, foiled Kafelnikov's attempt to win his first TMS event. In 1998, Rios prevailed over Andre Agassi in the final here and reached the top spot in the ATP rankings.
In the fourth round, Rios faces 16th-seeded Alex Corretja. The Spaniard outdueled No. 22 Hicham Arazi of Morocco, 4-6, 7-6 (7-3), 6-1.
Capriati, who reached the final here last year but squandered eight championship points, struggled to improve her match record to 12-2 this season. The contest was knotted at 1-1 in the final set when Capriati took five of the last six games.
Capriati claimed her second straight Australian Open crown in January and reached the final in Scottsdale last month.
Myskina, 20, also pushed Venus Williams to a third set in the quarterfinals of last month's Dubai Women's Open. On Sunday, she led Capriati by a set and 5-4 in the second but was unable to overcome her own errors.
Capriati encounters Uzbekistan's Iroda Tulyaganova, the 15th seed, who overcame Japan's Ai Sugiyama, the 24th seed, 3-6, 6-4, 7-5.
To continue the day of upsets on the men's side, Gaston Gaudio of Argentina knocked off No. 7 Sebastien Grosjean of France, 7-6 (9-7), 4-6, 6-1.
Gaudio will meet another unseeded player in the fourth round. Juan Ignacio Chela of Argentina eliminated No. 24 Nicolas Escude of France.
Also in the last 16, No. 8 Thomas Johansson of Sweden battles No. 9 Agassi in a meeting between the last two Australian Open champions. The ATP Champions Race leader, Johansson cruised past Guillermo Coria of Argentina, 6-1, 6-4. Agassi defeated another Argentine, Agustin Calleri, 6-3, 6-2.
No. 7 Jelena Dokic of Yugoslavia and No. 10 Meghann Shaughnessy of the United States were upset in the women's draw. Dokic fell to Luxembourg's Anne Kremer, the 26th seed, 6-3, 6-1, and Shaughnessy lost to fellow American Marissa Irvin, 4-6, 6-3, 6-4.
Kremer's fourth-round opponent is 12th-seeded Elena Dementieva of Russia, who got past 19th-seeded Barbara Schett of Austria, 7-6 (7-3), 6-2.
Irvin meets compatriot Serena Williams, the eighth seed, who crushed Katarina Srebotnik of Slovenia, 6-1, 6-0.
Defending champion and second seed Venus Williams -- Serena's sister -- was leading her third-round encounter with Mariana Diaz-Oliva, 6-2, 1-0, when the Argentine retired with a lower back injury. This marked Venus Williams' 20th straight match win at this event.
Venus Williams meets No. 14 Amanda Coetzer. The South African rallied past German Barbara Rittner, 2-6, 6-3, 7-5.
No. 3 Martina Hingis of Switzerland also enjoyed an easy passage to the fourth round, hammering Tatiana Poutchek of Belarus, 6-1, 6-0. The "Swiss Miss" goes up against American teenager Alexandra Stevenson, the 23rd seed, who knocked off Bulgaria's Magdalena Maleeva, the 16th seed, 6-3, 7-5.
Also advancing was fifth seed Monica Seles, the two-time former winner from the United States.
Seles has reached at least the semifinals in all seven tournaments she has played this year. In the fourth round here, she plays No. 9 Silvia Farina Elia of Italy, who recorded a 6-3, 6-2 rout of No. 18 Tamarine Tanasugarn of Thailand.
No. 4 Kim Clijsters of Belgium moved on with a 6-4, 6-4 win over Paola Suarez of Argentina. Clijsters' next opponent is unseeded Cara Black of Zimbabwe, who defeated Tina Pisnik of Slovenia, 6-3, 6-2.
Having the best season of her career, Israel's Anna Smashnova dropped 12 of the final 14 games to lose to No. 28 Tatiana Panova of Russia, 2-6, 7-5, 6-1.
Panova goes up against Spain's Arantxa Sanchez-Vicario. The 11th seed recorded a 6-2, 7-6 (7-2) win over American Lisa Raymond, the 17th seed.