By Joe Holley
Washington Post Staff Writer
Friday, February 22, 2008 12:30 PM

Sidney Watters Jr., who died Feb. 14 at age 90, was a Hall of Fame trainer with a slew of champion horses to his credit, but among racing aficionados of a certain age, he was almost as well known for what might have been.

The year was 1970, and the racing world was buzzing about Hoist the Flag, a sure bet to become Mr. Watters's first Kentucky Derby entry. Undefeated in four electrifying races as a 2-year-old, the horse began the next season by winning the Bay Shore Stakes in the incredible time of 1:21 for seven furlongs. The Triple Crown, the first since Citation in 1948, seemed likely.

"A lot of old trainers say he was the best horse they ever saw," said Dick Small, Mr. Watters's nephew and an acclaimed trainer himself.

A modest man not given to superlatives, Mr. Watters didn't say much about Hoist the Flag, but he knew he had found the horse of a lifetime. His wife was more effusive. "Hoist the Flag is so good, he's scary," Margaret Watters, who lived in Middleburg, told The Washington Post in spring 1971.

"Do we think about the Derby? We've got to be thinking about the Derby," she said. "But having a horse like that is tempting fate."

A few days later, fate intervened. Hoist the Flag was in the midst of a routine morning workout at Belmont Park in preparation for the Gotham Stakes when the sound of a sharp crack, as if a cold-stressed tree limb had snapped in winter, marked the end of his racing career. The once and future champion had shattered pastern and cannon bones in his right hind leg.

"He was my favorite," Mr. Watters told Thoroughbred Times many years later. "Just a marvelous, gentle horse who could do anything you wanted him to do."

Mr. Watters, who died of pneumonia and complications of Alzheimer's disease at Gilchrest Center for Hospice Care in Towson, was born in Baltimore. His father was a trainer, and he grew up around horses, fox hunting and racing. "Training horses was instinctive for him," Small said.

He won his first race as a steeplechase jockey at Saratoga at 16 and was named Saratoga's leading trainer at 70. As a rider, he won almost 50 races from 1935 to 1941, before his career was interrupted by World War II. Serving in the Army Air Forces, he flew 40 missions in the Pacific theater as a B-24 gunner.

Returning from the war, he trained steeplechasers and a few flat runners for Richard K. Mellon, heir to the Pittsburgh-based Mellon financial dynasty. Mr. Watters was the leading steeplechase trainer five times between 1948 and 1971 and also trained two jumping champions, Amber Diver in 1963 and Shadow Brook in 1971.

The New York Times described his training approach in a 1983 article: "He races them lightly, but they are fit and ready when they run. Watters has long been respected when sending out first-time starters and runners returning from long layoffs."

He captured the 1965 Pimlico Race Course training title with 14 wins. From 1976 to 1999, he registered 395 wins from 3,092 starters. From 1976 to 1999, his runners earned more than $12 million, according to Thoroughbred Times.

Mr. Watters was the trainer of the 1983 champion Slew o' Gold, a 3-year-old sired by Seattle Slew with almost as much potential as Hoist the Flag. In 1984, Slew o' Gold won the Jockey Club Gold Cup, Woodward Stakes and the Wood Memorial Stakes.

He also managed to breed a few of his own mares to Hoist the Flag and sell the resulting foals. For almost a decade, the horse who might have been was a valuable broodmare sire until his premature death as a 12-year-old in 1980, after he was kicked by a mare. "He had very brittle bones," Small said.

Mr. Watters, who was inducted into the National Museum of Racing and Hall of Fame in 2005, was a gentle man, his nephew said. "Racetracks are a pretty tough environment with everybody criticizing everybody else -- you know they're competing every day -- but nobody ever criticized him," Small said.

For many years, Mr. Watters lived year-round at New York's Belmont Park racetrack, in a bunkhouse between two barns. "He came back when all his old owners died off and faded away," his daughter, Nonie Watters, said. He spent the last years of his life at Dunmore Farm, near Monkton, Md., which has been in the Watters family for many years.

Small recalled how his uncle in recent years would stroll out to the pasture most days and his favorite horse, a large gray stallion named Big Diamond Jim, would come galloping to the fence from a half-mile away. "He loved all creatures -- horses, dogs, chickens, not just racehorses," Small said.

Mr. Watters's wife died in a riding accident in 1993.

Survivors, in addition to his daughter, of Leesburg, include a son, Eric Watters of Monkton.