By the standards of history, especially recent history, Saturday's Kentucky Derby field is a bad one.

None of the 13 entrants has given evidence of being an outstanding 3-year-old. None seems likely to achieve future greatness. Plugged Nickle and Rockhill Native, the cofavorites, merely would have been part of the Derby supporting cast in any of the last five years.

But it would be difficult to persuade many of the 125,000 spectators at Churchill Downs Saturday (WJLA-TV-7 5 p.m.), let alone the principals, that this is an inconsequential horse race. One of the special qualities of the Derby as a sporting event is that no running seems historically insignificant.

The most hard-core sports fans may forget who won the Super Bowl or the NBA championship five years earlier. But the names of even undistinguished Derby winners acquire a sort of immortality.

As a result, this race has a special meaning even for men who have spent a lifetime in the business, have won dozens of important races and ought to be blase about another one.

"You know," said Tom J. Kelly, the veteran trainer of Plugged Nickle, "I went to France last fall and the purser on the plane knew about every Derby for the last 20 years. I went to Argentina and people there knew about the Derby even if they didn't know about anything else. If I won this race, I'd be ready to swing the golf clubs for the rest of my life."

It is Kelly and Plugged Nickle who appear to have the edge in the 106th Derby. The colt has won important stakes races in his last three starts, he never has been beaten at a mile or farther, he seems to be coming up to the Derby in perfect physical condition.

Yet the times of his victories reveal how weak the current generation of 3-year-olds is. A top-class thoroughbred ought to be running 1 1/8 miles in 1:48 or thereabouts. Plugged Nickle won the Wood Memorial Stakes in 1:50 4/5; he won the Florida Derby in 1:50 1/5. So he appears more vulnerable than most Derby favorites.

In fact, he may not even be the favorite Saturday. Kentuckians may put their money where their hearts are; on Rockville Native, who is based in Lexington, who launched his career at Churchill Downs last summer, whose trainer Herb Stevens is the fourth generation of a Kentucky racing family.

Bred, so unimpressively that Stevens gelded him -- "I figured there are enough cheap stallions in the world" -- Rockhill Native overcame his pedigree and earned recognition as the best 2-year-old of 1979. But this year he has been an enigma. He ran two inexplicably dismal races in Florida, then came home and came back to life. When he won the Blue Grass Stakes at Keeneland last week (in 1:50), he established himself again as a solid Derby candidate.

Of the remaining 12 horses in the field, four can be considered legitimate contenders for the Derby's $239,300 first prize: Rumbo, Jaklin Klugman, Super Moment and Genuine Risk.

Rumbo was the second-best horse in California this winter, and the best one, Codex, wasn't nominated to the Derby. Even so, trainer Tom Bell didn't want to come here. He felt the colt still was too immature, but he was overruled by his owner.

"We call him Dumbo," said Bell's son, Ray, who accompanied the colt here. "All his problems are upstairs. He shies away from the whip. He ducks from dirt clods. He ducks away from other horses. He jumps tracks left by the starting gate. Eventually, he'll come out of it.If he doesn't pull his antics in the Derby, he'll win."

Super Moment, said Bell, "was 10 lengths inferior to Rumbo in California." But this is Kentucky, and last Thursday Super Moment closed strongly to finish two lengths behind Rockhill Native in the Blue Grass Stakes. Trainer Ron McAnally maintained that even when Super Moment was being soundly beaten on the West Coast, he was accelerating fast at the end of his races. The Derby's 1 1/4-mile distance will suit him.

Jaklin Klugman might have been the sentimental favorite in this Derby even if he weren't co-owned by popular actor Jack Klugman. By a nondescript sire, Orbit Ruler, whose stud fee was $500, out of a mare who broke down in a $12,000 claiming race, Jaklin Klugman would be the humblest animal to win the Derby in modern times.

Does he have a chance? "What did he win the other day, chopped herring?" his owner asked.In fact, the colt captured the one-mile Stepping Stone Purse at Churchill Downs in fairly impressive fashion, having previously established himself as one of the better 3-year-olds in California. He does have a chance.

Genuine Risk will be the first filly to run in the Derby since Silver Spoon in 1959. She could be the second filly ever to win it, along with Regret in 1915.

After capturing the first six races of her career, all against fillies, Genuine Risk lost by 1 1/2 lengths to Plugged Nickle in the Wood Memorial. Trainer LeRoy Jolley didn't want to come to Kentucky, but he evidently was overruled by his owners, and now he is putting on a brave front.

"This is a tough race for a filly to win," Jolley said, "but Genuine Risk has always demonstrated great determination. I think her race in the Wood will benefit her, and she has room for improvement."

The other starters are Bold 'N Rulling, Degenerate Jon, Gold Stage, Withholding, Execution's Reason, Tonka Wakhan and Hazard Duke. They are not serious contenders, and their owners might have been prudent to save the $7,500 entry fee and put them in less ambitious spots. But these horses are in the field, of course, because there is only one Kentucky Derby.