Even before the Case of the Missing Leg, the racing operation of owner Mike Gill was a prime topic of conversation at Gulfstream Park. But now bettors and rival horsemen are practically obsessed by the subject: Who is this man?

Gill and his trainer, Mark Shuman, have had a phenomenal season here, winning 37 races in 31 days, but they experienced a rare disappointment last week when their gelding, Casual Conflict, broke down during a race. After the 9-year-old was euthanized on the track, his body was taken to the backstretch, where a state veterinarian would perform an autopsy. Before the horse was examined, one of his legs had disappeared.

An inquiry by Gulfstream officials revealed that one of Gill's vets had amputated the limb. The owner explained that the intention was to discover the cause of the breakdown, describing this as "a common practice," and said his vet has a couple other limbs on ice.

Some knowledgeable racetrack people wondered whether Gill was trying to conceal evidence of illegal medication or treatment used on the horse. Or perhaps his explanation was accurate in revealing that he is an owner with a fanatical attention to the details of his business.

These possibilities pertain not only to the missing-leg affair, but to the entire Gill success story. Is he winning because he runs such a professional operation, or because he is using illegal drugs on his horses? Such suspicions have abounded, particularly in the last week or two, because of the sudden, radical improvements by horses who go into the Gill-Shuman barn.

Racing fans have seen this phenomenon all too often: A previously undistinguished trainer suddenly becomes a miracle worker -- as the late Oscar Barrera did in the early 1980s, as Frank Passero Jr. did when he won 14 straight races at Gulfstream in 1996. Then his "magic" suddenly disappears and he returns to obscurity.

There are significant differences between Mike Gill and the others. He's no buffoon; he's one of the savviest owners or trainers I have ever interviewed -- one attuned to almost every nuance of the game. And he is not going to return to obscurity. With the resources from his successful New Hampshire mortgage company, Gill is putting millions of dollars into the game. In addition to his virtually nonstop claiming, he went to a sale of 2-year-olds in Miami last week and bought 32 young prospects for a total of $2.9 million. His ambitions are limitless: "I want to be the best. I want to be number one in the country. I want to win an Eclipse Award. I want to win the Kentucky Derby."

Gill makes astute claims and enters his horses in the right races; rarely are they in a spot where they can't win. Every acquisition gets close medical attention. Gill regularly gives new acquisitions a myectomy -- a minor throat operation that improves their breathing. He gives them all blood tests. He treats them for the disease known as EPM (equine protozoal myeloencephalitis). He said he spares no expenses in the care of his horses: "I just paid $18,000 for oats I shipped in from Dublin. Who else does that?"

But can mere sound care account for the performances of recent winners such as Tasty Caberneigh and Cahill Kid?

Tasty Caberneigh ran at Gulfstream on Jan. 19 in a $40,000 claiming race when he was trained by the capable Steve Flint and ridden by Jerry Bailey; he tired and finished seventh. Gill claimed him that day.

Nineteen days later Tasty Caberneigh ran against the same class of horses.This time he dueled head-and-head for the lead in a suicidal pace, running the first half mile in 44 seconds flat. But when he was challenged in the stretch, he ran away from the field and won by nearly five lengths -- a stupefying form reversal.

What happened? "I can show you the blood test," Gill said. "The blood test is the map for every horse. His thyroid levels were almost at zero. We put him on thyroid powder."

Cahill Kid had made his first start after a nine-month layoff in a $14,000 claiming race Jan. 3; he opened an early lead then faded to lose by six lengths. When Gill claimed the gelding, trainer Allen Iwinski was not perturbed to lose a 5-year-old beset with serious physical problems.

But Iwinski was perturbed when Cahill Kid returned to the races last Thursday in another $14,000 claiming race and won by eight lengths, running six furlongs in 1:09 flat -- a performance closer to that of a stakes horse than a lowly claimer. What happened?

"We gave him a myectomy," Gill said, "and we treated him for EPM."

Iwinski scoffed at the explanation. He said Cahill Kid's suspensory ligaments were damaged, that he had chips in his knee and other ills. Can a throat operation cure those problems? Iwinski added, "I've done 20 of those myectomies and very few horses have improved."

Gill rejoined: "You claim a horse from these guys, they're like car salesmen. They don't want to explain to their owner why a horse came back and won by 10 lengths. So they say you're cheating."

Gill has been caught for drug violations. He received an extraordinary three-year suspension in 1995, when he was training his own horses at Rockingham Park and one of them tested positive for clenbuterol. Security officers raided his barn and found syringes, hypodermic needles and bottles of illegal drugs.

Other critics wondered why Gill brought veterinarian Leonard Patrick to Florida to work for him full time this winter. Patrick was convicted in U.S. District Court in connection with killing a horse for insurance purposes by injecting him with E.coli bacteria, although the conviction was overturned on procedural grounds. Racing officials have had their eyes on him this winter; on Monday, investigators searched Patrick's vehicle and took samples of the medications in his possession.

Gill insists that his operation is honest, and that he got back into racing after his three-year ban out of love of the game. "What's my motivation to cheat?" he asked. "I'll gross $100 million a year in my mortgage business. Here's my ambition: to be the best at anything I touch."

Although Gill is a persuasive and engaging man, the doubts associated with his horses' sudden improvements can't be easily dispelled. People outside the sport might wonder why it is suspicious that horses should improve after getting the thorough medical care that Gill gives them. The answer is that horses rarely improve so suddenly with simple good care. Occasionally a trainer might discover a horse's "hole card" and find the key for making him run much faster, but this happens once in a blue moon. Bill Mott is arguably the best horseman in America, but I doubt that in his entire career he has achieved as many training miracles as Gill and Shuman have in the last two weeks.

If Gill keeps on winning at his present rate, he is surely going to achieve some of his lofty goals; he will probably be the top race-winning owner in America this year. But it is unlikely that will dispel the cloud of suspicion surrounding his success.