SHANGHAI, China -- Even without a Grand Slam victory this season, Andre Agassi can still finish No. 1 in the world if things go his way at the season-ending Tennis Masters Cup.

Marat Safin, who also has a chance of finishing No. 1, opens the weeklong event Tuesday against Carlos Moya, one of three Spaniards in the elite eight-player field at the Shanghai New International Expo Center, which has been transformed into a 10,000-seat stadium.

"It will be the most important match,'' Safin said. "It will be the opening match and everybody will be nervous.''

The rest of the opening day program pits Wimbledon champion Lleyton Hewitt, currently atop the rankings, against Albert Costa of Spain, followed by Juan Carlos Ferrero of Spain against Roger Federer of Switzerland.

Hewitt, Safin, Moya and Costa are in the Red Group, with Agassi, Ferrero, Federer and Jiri Novak of the Czech Republic comprising the Gold Group.

After three matches in round-robin competition, the top two players in each group advance to the semifinals. The title match, with possibly the No. 1 ranking hanging in the balance, will be played Sunday.

In the Championship Race, Hewitt is only 88 points ahead of Agassi, while Safin is another 110 points further back. Any of the three could finish No. 1. The winner here can earn as many as 150 points besides pocketing $1.52 million in prize money.

"It's a little frustrating,'' Agassi said of his failure to win a Slam in 2002, yet still be in position to finish No. 1. "It speaks to how hard I've had to work this year ... I feel sort of proud of that accomplishment.''

In last year's Tennis Masters Cup, played in Sydney, Australia, Agassi lost two of his three round-robin matches, failing to qualify for the semifinals

"I was a shadow of where I am this time,'' he said. "It's been tough, a grind, not been easy. But, that being said, it's been a great year.''

Safin said the field is dangerous.

"They are not an easy group,'' Safin said. "It's a tough one. Everybody plays well. You have two options. One is to win it.''

The winner of each round-robin match receives 20 points, with 40 points going to each of the winners in the semifinals and 50 for the championship.

Hewitt overhauled defending champion Gustavo Kuerten in last year's Masters Cup, becoming the youngest man ever to hold the No. 1 ranking.

Kuerten lost all his matches in Sydney and finished at No. 2, followed by Agassi and Russia's Yevgeny Kafelnikov.