Not long ago, Maryland's thoroughbred tracks offered their fans some of the most monotonous and least competitive racing in the country.

Almost every race every day seemed to be dominated by the same three trainers: Bud Delp, Dick Dutrow and King Leatherbury. It was a foregone conclusion that they would finish 1-2-3 in the standings at every race meeting in the state. One year, in fact, they ranked 1-2-5 in the country in number of races won. That obviously didn't leave much room for other Maryland horsemen to win much of anything.

But in a slow and gradual fashion, the face of Maryland racing has changed profoundly. A horseplayer who had spent the last two years in Iceland and returned to Laurel today would scarcely recognize the game. Ron Alfano is battling Leatherbury for the training title. Dutrow has been ineffective. Delp isn't even here. And a number of young trainers with medium-sized operations, such as Ken Sumida, Jack Kousin, Bill Wolfendale and Robert Wheeler, have been doing some of the best work in their profession.

When the Big Three were so impregnable, such competition was impossible. Delp, Dutrow and Leatherbury had once been fiercely competitive with each other, but like other big businesses that dominate a market, they learned that their best interests lay in mutual cooperation.

Violating both the rules and the spirit of the racing game, they stopped claiming horses from each other, for the same reason that the biggest oil companies don't go after each other's corporate throats. Instead the Big Three took horses from weaker stables that didn't have the resources to fight back in a claiming war. Their domination scared good trainers with 20- and 30-horse stables out of the state, because they knew they couldn't battle the clique.

What happened to the Big Three? Perhaps their success made them a bit complacent. Dutrow has not been performing lately like the Dutrow who was the most gifted horseman in the state. After Delp trained the best horse in the world, Spectacular Bid, the idea of operating a barn full of $3,000 claimers at Bowie presumably seemed less appealing. He now spends his winters in New Orleans while his brother Dick runs a scaled-down Delp operation here.

Only Leatherbury has maintained a powerful, successful stable in Maryland and even he conceded, "Once, I'd take anything that had four legs. I've scaled down a little bit and maybe I'm a little more selective now."

Leatherbury pointed out that younger horsemen have had a chance to learn their lessons by observing the Big Three. "A lot of trainers are coming up now and patterning themselves after us," he said.

Dutrow served as the mentor of many aspiring young trainers who have now become significant forces in the state: Alfano, Scott Regan, Joe Devereux and Tom Caviness, among others. Alfano was even good enough and bold enough to challenge the Big Three head on, claiming horses from them while they were engaging in their cozy hands-off practices with each other.

The fact that Alfano could start with a small stable and work his way up through the ranks proved that the Big Three were not invincible and that an ambitious young trainer did not have to leave Maryland in order to become a success. So while there was once no interesting, competitive second tier of trainers to challenge the Big Three, the stable areas at Maryland tracks now seem full of talented young horsemen on their way up. For the good of racing in the state, nothing could be healthier.