Cure the Blues, who had seemed indomitable throughout his racing career, cracked under pressure today. The colt virtually slowed to a walk in the Aqueduct stretch, losing both the rich Wood Memorial Stakes and his credibility as a Kentucky Derby contender.

He finished a distant third behind Pleasant Colony and Highland Blade. But the instrument of his destruction was Noble Nashua, who ran the 1-to-5 favorite into the ground.

Rarely has the outcome of a horse race been so clearly affected by tactics. Every one of the 30,020 spectators here knew that Cure the Blues had a formidable advantage as the principal speed horse in the field, and figured to coast to a comfortable early lead. But Noble Nashua's trainer, Jose Martin, and his jockey, Angel Cordero Jr., knew this, too.

"You have to adjust to the situation," Martin said. "We came here to win. You don't hold back." So what Cordero did was warm up, Noble Nashua, hard, getting him primed to come flying out of the gate. The colt was so on edge that he broke through the gate prematurely. And when the race did start, he was in high gear.

On a very slow racing surface, Noble Nashua pressed Cure the Blues through the first quarter-mile in 22 4/5 seconds, the half in 45 4/5.Those times were utterly extraordinarly. When the brillantly fast Bold Forbes won the Wood on a much faster track in 1976, his fractions were 23 1/5, 46 flat. Once Cure the Blues was moving so fast, jockey Jacinto Vasquez had no way to apply the brakes.

While Cure the Blues was starting to draw away from his challenger on the backstretch, Pleasant Colony on the backstretch, Pleasant Colony was just biding his time. "I sat on my horse and waited for him to tgell me when he wanted to run," said Jeffrey Fell, who inherited the mount because of a suspension to Jorge Velasquez. "Around the half-mile pole, he started to pick up on the bit. And then the speed started coming back."

Indeed, it was hard to believe how suddenly Cure the Blues decelerated. Midway on the turn he looked as if he were capable of running all the way to Churchhill Downs. But by the time he had gone around the turn -- and this was the first two-turn race of his career -- he was finished. Pleasant Colony flew past him, en route to a three-length victory. Then Highland Blade flew past him. All Cure the Blues could accomplish was to save the bettors who had plunged $455,888 to show on him.

Pleasant Colony paid $27.40, $10 and $2.10. Higland Blade returned $10.20 and $2.10 and Cure the Blues paid $2.10 to show.

Pleasant Colony's victory may be dismissed in some quarters as something of a fluke, since he obviously benefited so greatly from the speed duel in front of him. He had an undistinguished record, having lost his last start, the Florida Derby, by 13 lengths. But his time for the 1 1/8 miles, 1:49 3/5, was exceptionally good, considering the track's slowness.

"This is the one to beat in the Kentucky Derby -- no one else!" trainer John Campo exclaimed. "I know a good horse when I see one. I've been around too many of them in my day.He won easing up, you hear me, easing up! I was told there was only one horse in this race. Cure the Cure the Blues.Well, they were wrong. There was one: Pleasant Colony. Velasquez has the ride in the Derby and we'll win."

Fell is committed to ride in the Derby on Proud Appeal, who handed Cure the Blues the first defeat of his career, by a nose two weeks ago. The result of the Wood makes it probable that Proud Appeal will be the favorite at Churchill Downs two weeks from today. And Cure the Blues, if he goes to Kentucky at all, will be an almost forgotten horse.