How often do you have two greats like this get together at their best?" trainer Bud Delp asked this morning. "It's like a Frazier-Ali fight."

Indeed, the Jockey Club Gold Cup at Belmont Park does have the flavor, the building sense of excitement, the drama of head-to-head confrontation that usually is associated with heavyweight championships.

In one corner, Affirmed, the best horse of his generation at the age of 2: the Triple Crown winner at 3; and now, at 4, the richest thoroughbred in history.

In the other corner, Spectacular Bid, the winner of 15 of his last 16 races, a brilliant record blemished only by his loss in the Belmont Stakes.

But there is one crucial sense in which the parallel between Saturday's race and a prize fight breaks down. Boxers fight under standardized conditions: 15 rounds, an 18-foot ring. Horses compete at varying distances, weights and track conditions, and sometimes those circumstances -- rather than the innate ability of the animals -- determine the outcome.

If America's two best racehorses had met in either of the first two legs of Belmont's fall championship series, the Marlboro Cup and the Woodward Stakes, Spectacular Bid probably would have had Affirmed at his mercy. But not on Saturday.Trainer Laz Barrera could not have devised more optimal circumstances for Affirmed to take on the greatest challenge of his career.

The Jockey Club Gold Cup is run at 1 1/2 miles, the distance at which Affirmed scored his most breathtaking victory (in the 1978 Belmont), and at which Bid suffered his one crushing defeat.

When Spectacular Bid lost the Belmont in June, he lost it to a rival, Coastal, who was coming off a sharp recent race. This is the textbook way to get a horse ready for 1 1/2 miles, and this is the way Barrera has prepared Affirmed. The Colts victory in the 1 3/4 mile Woodward Stakes here two weeks ago should have put him in optimum condition for the Gold Cup.

Spectacular Bid missed the Woodward because a fever set back his training slightly. So now he must go into his battle with Affirmed after a four-week layoff from competition.

Delp professes to be unconcerned. "I started training for this back in July, by galloping him a mile and a half and two miles. This horse is fit to go to the Rocky Mountains. He's trained up to this race better than any race he's been in."

Even if Delp is right, and Affirmed does not have an edge in conditioning, the 4-year-old will have a tactical edge as the race develops.

Five other horses have been entered in the Gold Cup -- Czaravich, Coastal, Silent Cal, Bowl Game and Gallant Best -- and two or three of them may be scratched. None of them has the speed to prevent Affirmed from taking the lead when he wants. Just as he did in his memorable duels with Alydar, he can set a comfortable pace and wait for Spectacular Bid to get into gear and challenge him.

Some handicappers expect that Spectacular Bid will battle with Affirmed head and head from the start to prevent this from happening. Delp says his jockey, Bill Shoemaker, "is the greatest judge of pace there is." But regardless of Shoemaker's intentions, Bid has not been breaking quickly all season, and he probably lacks the quickness to force Affirmed's hand early.

Spectacular Bid has only one edge over Affirmed on Saturday. He probably is the superior racehorse. Throughout his career he has displayed a degree of brilliance unmatched by any American thoroughbred since Secretariat.

He has consistently annihilated his competition, and done it while overcoming adversity -- a marked contrast to Affirmed, who always seems to be the beneficiary of good fortune:

If Spectacular Bid can overcome the disadvantages that face him in the Gold Cup, he will establish his greatness unequivocally, for all time.