Spectacular Bid has established himself as one of America's all-time great racehorses, and yet his career has one notable blemish. Unlike the other champions of recent years, he has never run the one supreme race that would be the capstone of his career.

Secretariat will always be remembered for his 31-length triumph in the Belmont Stakes. Affirmed's victory in the Belmont epitomized his indomitable spirit. Seattle Slew's effort in the Jockey Club Gold certified him as a top-class thoroughbred.

But Bid has never given such a memorable performance. In the most important races of his life -- his quest for the Triple Crown and his confrontation with Affirmed -- he suffered defeats. He ran his best races in California stakes last winter that aren't true championship events.

On Saturday, Spectacular Bid makes the penultimate appearance of his career and his last in a classic race: the $549,000 Jockey Club Gold Cup at Belmont Park. His admirers would love to see him show the full extent of his ability in the historic 1 1/2-mile event. Unfortunately, this is not likely to happen.

In the Gold Cup, like all his races during 1980, Bid has lacked an opponent worthy of himself, one who could force him to go all out. Bid probably could have thrashed horses like Affirmed and Seattle Slew, but he had the misfortune to be at his prime in one of racing's drabbest years. His opponents Saturday would be better suited to a mid-week allowance race at Belmont Park than the richest thoroughbred race ever run in North America.

Temperence Hill is the only horse in the Gold Cup field with a reputation, and he established that reputation at the expense of one of the weakest crops of 3-year-olds in years. The others in the lineup are nonentities: Instrument Landing, Novel Notion, Stiff Sentence, Silver Eagles and Ivory Hunter. The only thing positive that can be said for this field is that it is an improvement over the Woodward Stakes two weeks ago, when Bid went into the starting gate alone and "won" the first walkover in America since 1949.

Bid's only competition at Belmont will be himself. He could blow this field away, winning by 15 or 20 lengths, running somewhere near 2:26 over a track that has been rather slow all fall. Even without meaningful opposition, that would be an exciting superhorse performance. But neither trainer Bud Delp nor jockey Bill Shoemaker would be inclined to let him run this way. Horsemen prefer to get the job at hand done while asking the minimum effort from their horse, and Delp doesn't want Bid to earn too big a weight assignment when he ends his career in a handicap at the Meadowlands later this month.

"My only instructions to Shoe," Delp said, "will be to win the race. We're not looking to set any records."

So Spectacular Bid probably will win the Gold Cup in a relatively uninspiring fashion. It seems implausible but Bid is going to go through a historic campaign in which he wins 11 straight races, earns more than $15 million and sets four track records without generating a moment of high drama.