When a great horse loses a race, his defeat will be followed by an alibi as surely as night follows day. Rarely in the history of the sport has a trainer explained the downfall of a 1-to-5 shot be saying that, on the day in question, he just wasn't good enough.

So it was no surprise when the excuses started flying after Spectacular Bid's loss to Coastal in the Belmont Stakes Saturday. The instant analysis offered by CBS's commenators was that jockey Ron Franklin had blown it, making a premature move with Spectacular Bid and failing to conserve his energy in the 1 1/2-mile race.

Then trainer Bud Delp revealed that Spectacular Bid had hurt himself when he stepped on a safety pin the morning of the race. The pin was embedded an inch into the hoof, and left a bruise after Delp pulled it out. The trainer said he had given serious thought o scratching his horse from the third leg of the Triple Crown.

Obviously, the injury did not help Spectacular Bid in the Belmont, but whether it caused his defeat is highly debatable. If the colt were hurt, he would have shown some signs of it in his prerace warmup, and certainly in the early stages of the race. But he ran as he was supposed to for the first mile and one quarter. Evidently, the hoof only bothered him in the last two furlongs of the Belmont.

But even after the race, there was no evidence of any injury. "The horse came back all right," said Dr. Manny Gilman, veterinarian for the New York Racing Association. "He also cooled out all right in the testing barn, and he looked perfectly sound the next morning when he stepped onto the van."

If the theory that the safety pin caused Spectacular Bid's defeat is suspect, the notion that his jockey caused it is idiotic. Any time a front-running horse is beaten, second-guessers can (and will) say that the rider moved too soon. Whenever a stretch-runner is beaten, they will say that the jockey moved too late. These alibis can be applied to almost every horse who has never lost a race. They are usually wrong.

Franklin gave Spectacular Bid a ride on Saturday that was intelligent and tactically sound, compared with his usual performances. He got the horse into good position at the first turn, without losing much ground. He went for the lead early, which is often the thing to do in the Belmont. Most of the Belmonts in recent years have been captured by the front-runner.

Franklin did not push Spectacular Bid too fast too soon. His initial three-quarters of a mile in 1:11 1/5 should have been well within his capabilities.

The "excuse" for Spectacular Bid's poor performance in the Belmont might have been genetic: Perhaps he is not bred to run a mile and one half. To an American horseplayer, this notion might seem far-fetched, especially in view of the colt's strong finish in the 1 1/4-mile Kentucky Derby.

But in other parts of the world, particularly England, handicappers place a great emphasis on a horse's inherent distance capabilities, and they might view a good mile-and-a-quarter horse with some suspicion in a 1 1/2-mile race. Spectacular Bid just might be one of those horses who can't go the distance.

Or he might simply have lost the Belmont because he was tired from his tough campaign this spring. Certainly, his performance Saturday did not reflect his true ability. Having beaten Golden Act by six lengths in both the Kentucky Derby and the Preakness, Spectacular Bid could not hold him off for second place in the Belmont.

Every great horse has his record occasionally blemished by a defeat. Even Secretariat lost several races that he shouldn't have lost (His post-race excuses included a fever, a bad ride and an abscessed lip).

The fact that Spectacular Bid turned in one subpar effort after 12 straight brilliant victories hardly mars his reputation permanently. He has already proved his greatness, and he can be forgiven one defeat even if he doesn't have a legitimate alibi. CAPTION: Picture, Jockey Ron Franklin walks Spectacular Bid along Pimlico shed row after Belmont defeat. AP