Roger Laurin was watching over Chief's Crown at Keeneland one morning last week when the chaplain came on to the stable area public-address system to deliver the morning prayer. "Let not your heart be troubled . . . " he began.

The words might have been directed at Laurin, whose life as a trainer has been filled with stress and anxiety. He unwittingly gave up the chance to train the greatest horse of modern times. He endured crushing pressure in the most prestigious training post in America and finally lost the job. He has been subjected to a ceaseless barrage of criticism for his training of Chief's Crown.

Through these difficult times, Laurin has often been uptight, withdrawn, uncommunicative. Not long ago, a reporter came to him and said, "I've got to do an interview with you but everybody tells me you're pretty boring." Yet as the Kentucky Derby has approached and even the most carefree trainers start feeling knots in their stomachs, Laurin has become amiable, relaxed, even serene. For what may be one of the few times of his professional life, his heart is, indeed, untroubled.

Laurin was practically born into the training business. His father Lucien is a lifelong horseman, and Roger got his first trainer's license when he was 18. He started with cheap horses in New England and even spent a couple of winters in the cold and gloom of Bowie, Md., but he started making a reputation when he developed a good mare named Miss Cavandish. That success helped him win a prestigious job training for the Meadow Stable, but he soon was lured away by an offer no horseman could refuse.

Laurin was hired to train for the Ogden Phipps family, who had the greatest racing stable in America. It was more than a stable, it was a dynasty, with the Phipps' great stallion, Bold Ruler, begetting champions year after year.

When Laurin took over, he turned over the Meadow Stable horses to his father. In the barn was a 2-year-old named Riva Ridge, who was one week away from the first start of his career; on the farm was a yearling named Secretariat.

While Lucien was training these colts and winning back-to-back Kentucky Derbies and earning himself a niche in the Racing Hall of Fame, Roger was presiding over the sudden decline of a dynasty. It wasn't his fault, really; the aging Bold Ruler had ceased to be a prepotent stallion. But Laurin took all the heat.

Even in the best of times, working for the crusty patrician Phipps was an ordeal. In these bad times, the pressure must have been unbearable, and a friend of Laurin's said the experience was "crushing."

When Laurin finally left the Phipps job -- by mutual consent -- he formed a public stable, and over the years his performance was generally successful but hardly inspiring. Some New York racing people thought he displayed more enthusiasm for his golf game than for horses; few would have expected him to perform a masterpiece of training with Chief's Crown.

After the colt won the 2-year-old championship and was syndicated for $20 million last year, the whole racing world started scrutinizing Laurin's work this winter. It was hard to find a soul in Florida who liked what he saw. Chief's Crown isn't an impressive-looking animal; his style of running isn't especially fluid and he sometimes makes funny noises when he trains. Clockers and trainers were saying that the colt was lame before he made his first start of the season -- and won.

After that one sprint, Laurin sent Chief's Crown into the Flamingo Stakes with seemingly little preparation. Rival John Veitch, the trainer of Proud Truth, declared that Chief's Crown couldn't possibly be fit enough to win at 1 1/8 miles. Chief's Crown proceeded to lead all the way and beat Proud Truth by a length.

At the time, Laurin bristled at the criticism and second-guessing; his attitude toward the press became almost Nixonian. But after the Flamingo victory had proved all his detractors wrong, he came to Kentucky with a perceptibly different frame of mind, an air of relaxed self-confidence.

Asked about the light, seemingly inadequate training regimen Chief's Crown had in Florida, he now could discuss his methods without feeling defensive. "The game plan from this horse's 2-year-old year has been to bring him along slowly. Once he's proved he's a champion, there's no point proving it every single day. He doesn't have to have a lot of fast workouts, anyway, because he gallops a little different from most horses and gets a lot out of them."

Chief's Crown had only one fast work between the Flamingo and the Blue Grass Stakes, but he won the Keeneland stake with ease. When he completed his final prep for the Derby, it was finally apparent that Laurin had accomplished something extraordinary.

It was not that he had guided Chief's Crown to three straight victories, but rather that he had done it without taking a physical toll on the horse. In the famous words of trainer Horatio Luro, he had not "squeezed the lemon." He will come into the Kentucky Derby with a fresh, fit horse who is ready to deliver the best race of his life.

Laurin knows this, and that is why he seems the most relaxed, confident trainer at Churchill Downs this week. "I'd feel pressure if I didn't have so much confidence in the horse," he said. "But now it's the other guys' turn to get nervous."