The Swiss teenager captured her third straight Australian Open title in January, but put forth back-to-back embarrassing performances in the next two Grand Slam events.

Hingis let her temper get the best of her in her three-set loss to the now-retired Steffi Graf in the French Open final and followed that up with a humiliating 6-2, 6-0 first-round defeat to Australian teenager Jelena Dokic at Wimbledon.

But Hingis has regained her focus since that tumultuous time and won three tournaments, reached the final of three others, including the U.S. Open, and reclaimed the No. 1 ranking from Lindsay Davenport.

Hingis also has seen American sisters Venus and Serena Williams emerge as legitimate threats to her No. 1 ranking. Venus has beaten Hingis three times in five meetings this season and Serena defeated Hingis in the U.S. Open final.

Overall, Hingis has won a WTA Tour-leading seven titles in 1999, but has come up short in the last two finals she has appeared in. She lost to Venus Williams in her homeland tournament in Zurich last month and fell to Davenport in Sunday's final of the Advanta Championships in Philadelphia.

Hingis defeated the then top-ranked Davenport in four sets in last year's season finale and will open defense of her title against Sandrine Testud of France on Tuesday night.

Davenport enters the season-ending tournament with some much-needed confidence after her victory over Hingis on Sunday. Sidelined for the past month with a left wrist injury she aggravated at Filderstadt, Germany last month, she looked strong last week in Philadelphia, dropping only one set en route to the title.

Davenport defeated Graf in the Wimbledon final for her second career Grand Slam title and has won six tournaments overall, matching her total of 1998.

One of Davenport's stunning losses came at the Australian Open, where she lost to Amelie Mauresmo of France in the semifinals. Davenport has beaten her twice since then and will look to make it three in a row when she faces Mauresmo on Wednesday night.

Third seed Venus Williams will be making her debut at the year-end event after a knee injury sidelined her last year. She has won six tournaments this season and cracked the top five in the WTA rankings.

But Venus watched her younger sibling steal the spotlight at the U.S. Open as Serena became the first Williams sister to win a Grand Slam singles title. In addition, Serena finally beat her sister for the first time over a month later in the Grand Slam Cup final.

Coming off a horrible 6-1, 6-2 loss to Davenport in Philadelphia, Venus will look to bounce back on Wednesday night against Conchita Martinez of Spain.

Serena Williams will be returning to the city of her greatest triumph as she makes her debut at the Chase Championships. She eliminated Davenport in the U.S. Open semifinals before defeating Hingis in the final.

The 18-year-old Serena has joined Venus in the top five in the rankings after winning the first five singles titles of her career. She has put together an impressive 41-7 record this season, which includes two 16-match winning streaks.

Serena Williams, seeded fourth, will take on Dominique Van Roost of Belgium in the first round on Tuesday night. She is on the opposite side of the draw from her older sister.

Tonight's opening-round action will feature fifth seed Mary Pierce of France against Russian teenager Anna Kournikova and seventh seed Barbara Schett of Austria taking on Arantxa Sanchez-Vicario of Spain.

After winning four titles in 1998, Pierce failed to come out on top in four finals this season before claiming her first crown of the year at Linz, Austria three weeks ago.

Pierce defeated Martina Hingis here two years ago en route to the final, but lost to Hingis in last year's quarterfinals. She could face Hingis again in the next round.

Kournikova has battled through injury and coaching instability to qualify for the season-ending tournament for the second straight year.

Kournikova fired coach Pavel Slozil at the Lipton Championships and reached her only final of the year at the Family Circle Cup in April, losing to Hingis. She suffered a stress fracture in her foot during practice in July and missed the summer hardcourt season, including the U.S. Open, and has gone 3-3 since returning to action.

Schett will be making her initial appearance at the year-end tournament, thanks to a breakout year that has seen her compile a 46-24 record. Despite her impressive record, she reached her first final of the season at the Ladies Kremlin Cup in Moscow three weeks ago.

Sanchez-Vicario secured the 16th and final spot in the field after Amy Frazier lost to Hingis in Philadelphia. The Spaniard will be making her 11th appearance at the season-ending tournament, with her best result coming in 1993 when she lost to Graf in the final.

In other first-round matchups, sixth seed Nathalie Tauziat of France, who has won two titles in the indoor season, will take on Amanda Coetzer of South Africa on Tuesday, and eighth seed Julie Halard-Decugis of France will make her first appearance at the year-end event since 1994 when she meets 1995 runner-up Anke Huber of Germany on Wednesday.

Graf, a five-time champion, will be honored in a retirement ceremony on Tuesday night. Jana Novotna, the 1997 champion, also will be feted during the tournament after retiring from active competition last month.

This event offers the only best-of-five sets final in women's tennis. First prize is $500,000.