Indomitable as ever in head-to-head competition, Affirmed beat Spectacular Bid today and reached the zenith of a brilliant career.

He captured the $375,000 Jockey Club Gold Cup by three-quarters of a length over his younger challenger, with Coastal another three lengths behind.

He proved his superiority in a frantic stretch drive that the 36,187 spectators at Belmont Park will long remember, but it was the relatively tame first half-mile of the race that largely determined its outcome.

Affirmed came into this long awaited showdown with the same edge he had possessed in his memorable Triple Crown victories over Alydar last year.

As the only speed horse in the race, he could set his own pace and force Spectacular Bid to alter his normal running style.

His jockey, Laffit Pincay Jr., knew this well, so he broke from the gate sharply. When he saw that Bid wasn't making an immediate challenge, he took his mount under restraint and let him coast.

He covered the first-quarter mile in 25 seconds, time more suitable for cheap claiming horses than champions, and the half in 49, with Bid a length behind him. Pincay was pleased but not surprised. "I expected Bid to stay behind me even when it was slow," he said.

From that point, the Gold Cup had been transformed from a true 1 1/2 mile test into a one-mile race in which Affirmed had a one-length head start.

Bill Shoemaker, on Spectacular Bid, wasn't going to wait any longer. He started urging his mount ahead, but Affirmed maintained his narrow advantage even while Pincay was sitting practically motionless.

They increased the tempo as they ran down the backstretch, covering six furlongs in 1:131/5 and a mile in 1:371/5, when suddenly Affirmed seemed to take command.

He spurted ahead, and Bid dropped briefly out of contention. Shoemaker was mystified. "At the half-mile pole," the veteran said, "he just spit out the bit."

In fact, it appeared that Coastal, not Bid, was going to be Affirmed's principal challenger. He rushed up along the rail -- just as he had done when he won the Belmont Stakes in June -- and Ruben Hernandez started thinking that he had a shot to pull an upset that would live in racing history.

Pincay knew better. He still hadn't even asked Affirmed for any serious running. He would dispose of Coastal's brief challenge with ease, but as he did, Spectacular Bid seemed to find himself again.

"He took hold of the bit about the quarter pole," Shoemaker said, and from there the jockey started whipping left-handed, making the decisive challenge that racing fans have been eagerly anticipating for months.

But they were playing Affirmed's game. Spectacular Bid had won 15 of his last 16 starts by making one big whoosh around his rivals, but Affirmed relishes head-to-head combat.

And even when Spectacular Bid was driving furiously at him, he gave the same unmistakable impression that he did in last year's Triple Crown races: he was not going to let any horse pass him.

Spectacular Bid couldn't get any closer than a half-length or so and they drove through a final quarter 1 1/2 miles in 2:27 2/5, excellent time over a dull racing strip. From the standpoint of time, it was probably the best performance of his career.

Affirmed paid $3.20 and $2.10 in Spectacular Bid, who had gone to the post at 7 to 5, returned $2.10 to place. There was no show betting in the four-horse field.

The Gold Cup was full of statistical milestones for the winners. Affirmed earned $225,000 to become the first horse to earn more than $1 million in a single season.

Pincay boosted his earnings for the year to $6.3 million and set a record in that department. The earnings of trainer Laz Barrera's horses reached $3.3 million for the year, breaking the mark he set last year.

These statistics will be quickly forgotten. What history will remember about the 1979 Jockey Club Gold Cup is that Affirmed seemed to prove he is a better horse than Spectacular Bid.

There will be no chance for a rematch. Barrera said his colt may run once more before he is retired this fall, but that a match race between the two colts would be pointless.

"I don't want to insult anybody or be called prejudiced," Barrera said, "but I think this is the best horse I ever saw."