Pleasant Colony can virtually clinch the horse-of-the-year title if he wins the Marlboro Cup at Belmont Park today. His task won't be easy, for he must face the real horse of the year, the best thoroughbred on this continent, in the $400,000 event.

This is, admittedly, a minority opinion, but Pleasant Colony isn't even in the same league with the 4-year-old colt Fappiano. In fact, Fappiano's best performances merit comparison with great horses such as Dr. Fager, Seattle Slew and Affirmed rather than with the 1981 Kentucky Derby winner.

But with his career almost over, Fappiano has not demonstrated to the general public or to more than a handful of racing cognoscenti just how talented he is. He has been a victim of some bad fortune and, perhaps, overly conservative management. Now he doesn't have much time left to fulfill his potential.

"He'll do it on Saturday," trainer Jan Nerud promised.

On Memorial Day, Fappiano won the prestigious Metropolitan Handicap at Belmont with a sensational performance, running a mile in 1:33 4/5 and trouncing the best older horses in the country. He was favored to win the 1 1/4-mile Suburban Handicap in his next start, but he was beaten by a length on a sloppy track.

"He couldn't handle the mud and he pulled a tendon in his leg," Nerud said. The injury knocked him out of competition for nearly two months, but when he ran in the one-mile Forego Handicap three weeks ago, he was as good as ever. Fappiano went head-and-head between horses all the way, speeding the first three quarters of a mile in 1:08 4/5, but was unfazed by what should have been a suicidal pace and won with authority, missing the track record by one-fifth of a second.

There are many horses who have been brilliant milers but cannot go a mile and one quarter successfully. Fappiano has not yet proved that he can handle the Marlboro Cup distance. But Nerud believes he can, and he skipped the shorter Woodward Stakes two weeks ago (where he would have been an absolute certainty to beat Pleasant Colony) in order to point for this race.

"I believe sincerely that he can go a mile and a quarter," Nerud said. "He can be rated. He can relax when he comes out of the gate. And he only got beat a length in the Suburban in a race where he got hurt."

Still, it is the Marlboro distance that is Pleasant Colony's edge Saturday. He is too slow to be effective at one mile; he may not have the staying power for a mile and a half. But, as he demonstrated in the Kentucky Derby, he is perfectedly suited for 1 1/4 miles.

His trainer, John Campo, is highly confident, much more than he was before Pleasant Colony defeated older horses for the first time in the Woodward Stakes two weeks ago. "He has come up to the race better than he did the Woodward, really," Campo said. "It's unbelievable how well he's doing. I'm not worried about anything."

Campo surely doesn't have to worry about the distance or his horse's condition or his other principal rivals: Amber Pass, Temperence Hill and Noble Nashua. But he would be advised to worry a great deal about Fappiano.