At the start of the year, this generation of 3-year-olds appeared to be rich and deep in talent. The 1982 Triple Crown series figured to be one of the most interesting and competitive in years.

Unfortunately, this assessment has proved incorrect. One potentially good horse after another has been crossed off the list of Kentucky Derby contenders.

Deputy Minister, the 2-year-old champion of last season, turned out to be grossly overrated. So did D'Accord, another colt who looked impressive in the fall. Stalwart, the best 2-year-old on the West Coast last season, was hurt and had to be retired. Aloma's Ruler, who showed great promise in Florida this winter, was hurt and knocked out of training. Distinctive Pro and Shimatoree, two colts blessed with great speed, turned out to be nothing more than sprinters.

But the greatest disappointment of all was Star Gallant, who suffered the first defeat of his career to Timely Writer in the Florida Derby. He had displayed great speed and seemingly limitless potential in the first four starts of his career. But on Saturday he looked very much like a horse who cannot go 1 1/8 miles. While it may seem premature or unfair to write off a horse after only one defeat, it now seems difficult to imagine Star Gallant winning at the Derby distance of 1 1/4 miles.

As I tried to compile a list of bona fide Derby contenders (which a month before the race usually would include 10 or 20 names) I couldn't find many horses whom I could imagine winning at 1 1/4 miles. There are only four names on the list.

1. TIMELY WRITER is no superhorse, but he has displayed almost every virtue one could want of a Derby candidate. He is a paragon of consistency. He has the stamina to run 1 1/4 miles, but he is no plodder; Timely Writer can accelerate when his jockey wants him to take control of a race. Trainer Dominic Imprescia has no prior experience at this level of the game, but he seems confident and unfazed by pressure. Timely Writer is definitely the horse to beat on the first Saturday in May.

2. EL BABA has won eight of his nine career starts, and avenged the only defeat when he defeated Linkage in the Louisiana Derby a week ago. But because he spent the winter at the Fair Grounds, out of the mainstream of 3-year-old competition, he poses a problem for handicappers. The times of his races appear to be creditable, his overall record is admirable, and Marylanders will remember his rival Linkage as a good racehorse, but it is still too early to know how good El Baba may be.

3. AIR FORBES WON remained unbeaten when he scored a three-length victory over Shimatoree in the Gotham Stakes at Aqueduct. Still, the colt hasn't proved much in his three-race career. He beat nonentities in his first two starts, and won so easily on Saturday because Shimatoree was running out of oxygen in the last furlong of the mile race. While New Yorkers' enthusiasm for the colt is still somewhat premature, he could stamp himself as a legitimate Derby contender if he looks impressive April 17 in the Wood Memorial Stakes.

4. LINKAGE, like El Baba, is something of an enigma because he has spent the winter in New Orleans. But he is a far more dubious candidate because his archconservative trainer, the veteran Henry Clark, doesn't want to run in the Kentucky Derby. He wants to aim for the Preakness instead. If Linkage should win the Blue Grass Stakes at Keeneland, Clark will be under public pressure to go to Churchill Downs, but even so, horses don't often win the Derby when they are sent there as an afterthought.

While the credentials of some of these contenders are uncertain, the credentials of some other Derby candidates are spurious. Undefeated Advance Man, who will be favored to win the Arkansas Derby next weekend, isn't anything special. Neither is Muttering, the winner of Sunday's Santa Anita Derby. Neither is D'Accord, who still has some fans in Kentucky. A lot can happen in the four weeks before the Derby, but if no new stars emerge, Timely Writer will have a much easier task than anyone could have imagined just a few weeks ago.