The nation's top male racehorse and its top filly will run at Belmont Park on its Breeders' Cup Preview Weekend. So, too, will the 2-year-old who has been touted as the sport's next big star.

But none of these horses--Behrens, Silverbulletday and More Than Ready--is a cinch to win. The weekend's races are intriguing tests, not merely preps for the sport's championship day at Gulfstream Park Nov. 6.

More Than Ready looked like a budding superstar as he won the first five starts of his career during the spring and summer. His admirers thought he might be the best American 2-year-old of the 1990s. But a fever disrupted his racing schedule in August, and when he returned to competition he was narrowly beaten in the Futurity Stakes at Belmont. Was he still feeling the lingering effects of an illness, or had More Than Ready been overrated? That question will be answered in the prestigious Champagne Stakes Saturday.

It's a tough test. More Than Ready's rivals include trainer Wayne Lukas's top 2-year-old, High Yield, who won the Hopeful Stakes at Saratoga by five lengths, and Chief Seattle, who might have won the Futurity but for a difficult trip. If he can beat this tough field, More Than Ready will set the stage for a much-awaited showdown with the California star Forest Camp in the Breeders' Cup Juvenile.

Behrens is the headliner on Sunday's card, the favorite to win the $1 million Jockey Club Gold Cup. By winning four of his last five starts, while the country's other top older runners were sidelined by injuries, he is the leading contender for the horse-of-the-year title. Trainer James Bond freshened Behrens so he would be sharp for the Gold Cup and the Breeders' Cup Classic, but some handicappers wonder how effective he will be running 1 1/4 miles after a 10-week layoff. Bond, however, exudes confidence. "He's been awesome," the trainer said. "Everything he's showing me is very positive."

Behrens can't afford a subpar effort. His rivals include River Keen and Almutawakel, the 1-2 finishers in the Woodward Stakes; and the 3-year-old Lemon Drop Kid and Vision and Verse, the top two finishers in the Belmont Stakes who are facing older rivals for the first time.

Silverbulletday, the brilliant 3-year-old filly who has won 14 of her 16 career starts, is also facing older rivals for the first time. She has easily dominated members of her own age group, but will face a formidable challenge from the 4-year-old Beautiful Pleasure in the Beldame Stakes.

Other stakes on the weekend schedule are the $600,000 Turf Classic Invitational Saturday, and the Frizette Stakes for 2-year-old fillies Sunday.