Even the California loyalists agreed this winter that there wasn't a single solid Kentucky Derby contender on the West Coast. Then a colt named Croeso, who might have been the 10th-best 3-year-old in the West, traveled to the Florida Derby and beat all the prominent Derby-age colts in the East.

His victory provided strong evidence that there aren't any good 3-year-olds anywhere, that the 1983 crop is the weakest in years. That impression is confirmed by the fact that the favorite in future-book betting on the Derby in Las Vegas is Copelan, an animal who would need a respirator to go a mile and a quarter. Copelan will not be in the winner's circle on the first Saturday in May. But who will?

In a year like this, racing fans tend to look for late bloomers, colts who start to show signs of brilliance in the weeks before the Derby. But history shows clearly that horses of this type don't succeed at Churchill Downs. In the absence of a standout like Affirmed or Spectacular Bid, the Derby winner will be a horse who showed some ability as a 2-year-old and who has a pedigree and stretch-running style that will enable him to succeed at 1 1/4 miles. The last three Derby winners--Gato del Sol, Pleasant Colony and Genuine Risk--all fit this description.

There are at least a half-dozen colts who fill the mold this season--solid if uninspiring animals who were decent 2-year-olds and seem likely to handle the Derby distance:

Fifth Division is considered the best 3-year-old in California by the cognoscenti there, now that the champion colt Roving Boy is sidelined by an injury. Fifth Division ran a respectable third behind Roving Boy in the rich Hollywood Futurity last fall, and he has been training well for his 1983 debut. A son of the long-winded Fifth Marine, he is bred to run a distance.

Desert Wine finished second to Roving Boy three times last year, and looked good winning his first start as a 3-year-old. "If they ran the Derby tomorrow," said Pimlico General Manager Chick Lang, "he'd be the favorite." Maybe. But the pedigree experts question whether 1 1/4 miles will be his game.

I Enclose gave one of the most impressive performances by any 2-year-old last season when he won the Nashua Stakes at Aqueduct. He hasn't raced yet this season, but his capable trainer Eddie Kelly is getting him ready in Florida.

Cast Party closed strongly to win the Laurel Futurity last fall and looked like a horse who will get better as the distances get longer. A minor ailment knocked him out of the Florida Derby, but he is expected to run in the Flamingo Stakes at Hialeah.

There are a number of other capable 2-year-olds from last season who have the potential to win the Derby--Pax in Bello, Slewpy, Highland Park--but none of them has evoked rhapsodies from racing fans. On each coast, however, there are colts who are generating excitement, even if they don't happen to fit the model of a Kentucky Derby winner.

But excitement can evaporate in a hurry. Silent Fox attracted a lot of attention before he ever set foot on a race track, because he is a full brother to Affirmed. He won a sprint in his first start, then captured a 1 1/l6-mile allowance race at Santa Anita in a manner that brought back memories of his brother. When a rival moved outside him in midstretch and looked like a winner, Silent Fox fought back tenaciously and won a photo finish, the way Affirmed used to do against Alydar. Of course, Silent Fox has not been tested against top-class 3-year-olds--and he won't be. Silent Fox fractured his right knee in a workout Saturday, and trainer Laz Barrera declared him out for the year.

Strike Gold has at least three strikes against him as a Derby contender. He is a one-dimensional front-runner. He may not have the pedigree for a mile and a quarter. He didn't race at all as a 2-year-old. But he is probably the most brilliant member of his generation. He looked awesome scoring the third straight victory of his career in the seven-furlong Bay Shore Stakes at Aqueduct on Sunday. His route-running ability will be tested in the coming weeks, but if he can carry his speed a distance he will win the Kentucky Derby.