Angel Cordero Jr.'s victory in the Gazelle Handicap Wednesday certainly won't be remembered as one of the landmarks of his career. After all, the jockey has won 5,648 other races. He has captured all of the Triple Crown events. He has won the Eclipse Award.

But none of his more celebrated triumphs demonstrated his skills more clearly than did his victory aboard the filly Kamikaze Rick at Belmont Park. The race offered persuasive evidence that Cordero, at 42, is still the best and smartest rider in the United States. And it was all the more convincing because his victim in the Gazelle was the jockey who eventually will take his place at the zenith of their profession -- Pat Day.

Those of us who are Cordero's ardent fans had begun to suspect last year that his skills were slipping, and that Day already had supplanted him. In a couple of key head-to-head confrontations at Saratoga in 1984, Day clearly outsmarted him and outrode him. Then, in the year's biggest race, the $3 million Breeders' Cup, Day gave a masterful performance on the longshot Wild Again, beating Cordero on the favorite Slew o' Gold.

Were Cordero's skills starting to decline? Was he about to become another Bill Shoemaker, living off his reputation? He has refuted these notions with excellent performances throughout 1985, and on Wednesday he had the satisfaction of showing Pat Day who's still the boss.

It was opening day at Belmont Park, and neither fans nor riders could know for sure what the racing surface was going to be like. But Cordero is a keen student of tracks and their tendencies, and he perceived quickly that being on the rail was a disadvantage. Solid favorites were bogging down when they raced on the inside, and horses who made moves on the outside were winning.

In the Gazelle, Cordero was riding Kamikaze Rick, a very fast sprinter who was attempting to go 1 1/8 miles. Day was on Overwhelming, who figured to be Kamikaze Rick's closest pursuer.

Kamikaze Rick broke on top, as expected, and Cordero opened a one-length lead, nursing the filly along through an easy first quarter in 23 seconds.

Ordinarily, he would have dropped to the rail so he could save ground on the turn and force his rivals to come around him. But on this track he had different ideas. He kept his mount far from the rail -- giving the other fillies plenty of room to drive up inside him.

Koluctoo's Jill, with Jose Santos aboard, was on the rail, chasing the leader, and Overwhelming was just outside her. They would have had to alter their courses drastically to get outside Kamikaze Rick, and so they had no choice but to challenge on the inside.

They moved inside the frontrunner on the turn, but Cordero had managed to set a slow pace and he still had a strong horse underneath him. He accelerated a bit, and Koluctoo's Jill dropped back along the rail. Now Overwhelmingly was the only remaining challenger, and Cordero had her right where he wanted her -- inside him.

As he turned into the stretch, Cordero let Kamikaze Rick drift toward the inside just a bit -- just enough to pin Day on the rail. Overwhelming figured to be the stronger horse at this point, and she drew abreast of Kamikaze Rick, but she couldn't get past. The disadvantage of being on the rail was insurmountable. Overwhelming weakened in the final yards, and Kamikaze Rick drew away to a 1 1/4-length victory that was entirely the doing of her jockey.

This is what makes Cordero the greatest tactician in his profession: he not only knows the optimal way to ride his own horse, but he has the skill to dictate the whole development of a race and influence the way rival jockeys ride their mounts.

Sometimes -- as in the controversial Preakness involving Codex and Genuine Risk -- he dominates the action in a bullying fashion. But as he showed Wednesday, he also can do with the subtlety of a chess master luring an opponent into a fatal move. Pat Day and all the other up-and-coming younger riders in America will have to wait a while longer before they wear Cordero's mantle.