The chance to compete in the Triple Crown comes only once in a horse's lifetime and, sometimes, only once for his trainer and owner. The now-or-never character of these races can create special problems and irresistible temptations for people with good 3-year-olds.

And so, on Saturday afternoon, trainer Butch Lenzini will do something that he probably shouldn't be doing. With mixed emotions, he will be saddling his talented colt, Aloma's Ruler, to run in the Preakness. In one moment, Lenzini will exude optimism about his chances. In another, he will confess, "I don't like to rush horses, and I've never done to a horse what I've done to him."

Aloma's Ruler probably has as much ability as any horse in the Preakness field, including the odds-on favorite, Linkage. When he made his 3-year-old debut in the Bahamas Stakes at Hialeah this winter, and won it with a brilliant performance, owner Nathan Scherr started thinking about the Kentucky Derby, the Preakness and the Belmont Stakes.

But a short time after that victory, Lenzini walked into the colt's stall and gasped when he saw that his ankle had blown up like a balloon. When he looked at the X-rays, he accepted the fact that all his hopes for the Triple Crown races had blown up, too. Scherr didn't.

"He wouldn't let himself believe that something was wrong," Lenzini said. "He said the horse should run in the Flamingo Stakes. I said no way. We battled tooth and nail."

Prodded by Scherr, Lenzini put Aloma's Ruler back into training sooner than he would have liked, and ran the colt in an allowance race at Pimlico two weeks ago. When he lost by a nose against a nondescript field, Scherr told his trainer, "I'm going to leave you alone."

Even so, Lenzini said, "I met the man halfway." He gave Aloma's Ruler another chance, entering him in the one-mile Withers Stakes at Aqueduct, a move that seemed ridiculously ambitious in view of the colt's previous performance.

Aloma's Ruler was sensational. He dueled with another fast Maryland horse, Shimatoree, raced him into defeat, then held off a stretch runner's challenge to win in 1:35 2/5. He fully verified Lenzini's high opinion of him. But his performance did not necessarily demonstrate that he is ready to win the Preakness.

Just as a human runner needs a foundation of extensive training and competition to compete in a marathon, a horse needs what racetrackers call "bottom" to run in the 3-year-olds classics. Aloma's Ruler doesn't appear to have it.

Even if the field for the 107th Preakness is not an exceptional one, Aloma's Ruler is meeting tough, seasoned horses, all of whom have run a succession of distance races this spring, and most of whom went through the 1 1/4-mile Derby grind. In contrast to them, Aloma's Ruler has run a total of three times in the last seven months.

"We're coming into the race on a shoestring," Lenzini conceded. "Even if he wins the Preakness, he won't be showing how good he is. In the Travers (at Saratoga in August), he will."

The danger in coming into a tough race with such thin preparation is that a horse can be hurt or so exhausted by the effort that his subsequent training and racing will be adversely affected. Lenzini is a very capable young trainer, and he has weighed the negative possibilities. "I know I made a mistake pushing him already, but I think we're over the hump. I think the worst that can happen is that he'll get tired."

Lenzini expects that even if Aloma's Ruler does not win on Saturday, he will run a very respectable race and emerge from the Preakness in decent physical condition. Realistically, that is the most he can hope for.