Judging from the current crop of 2-year-olds, we're not improving the breed of thoroughbreds. In fact, the species seems to have regressed. Of the more than 38,000 horses who were born into this equine generation, not a single one has looked like a genuine star. Mediocrity reigns. Since I started compiling speed figures in 1970, the winning performances in major 2-year-old stakes hae never been so slow as they have been in 1984.

The trend is likely to continue this afternoon, in the $262,550 Selima Stakes for fillies at Laurel and the $336,000 Champagne Stakes for colts at Aqueduct. In each of these races, the favorite has such shaky credentials that I would love to bet against the horse. But in each event, the quality of the competition is so poor that it is hard to make a positive case for anybody.

The Maryland-based colt Mighty Appealing takes his unbeaten record to New York, where he will be an odds-on favorite. On the surface, his credentials are dazzling. Trainer Dean Gaudet's colt has won all three of his races, by a combined total of 27 1/2 lengths. But everything that could possibly go right for Mighty Appealing did go right. In his first two starts he was able to take a comfortable early lead without being challenged. When he won the rich Laurel Futurity, he saved ground, slipping through on the rail on the turn while many of his rivals were going very wide. Even with optimal racing luck, his winning time wasn't impressive.

Mighty Appealing still hasn't shown that he can deal with adversity, but he probably won't have to today. The five challengers make a mockery of the Champagne's great tradition. Two are former claiming horses, and only one of the others has won even a minor stake. Mighty Appealing should solidify his claim to being the best colt of his generation.

Another youngster with a perfect three-for-three record, Charleston Rag, will be the heavy favorite at Laurel today (post time 4:32 p.m.). But her credentials are so spurious that it's worth taking a stab at one of the other six fillies in the field.

Charleston Rag won the prestigious Frizette Stakes at Belmont by 5 3/4 lengths in her last start. That might sound impressive -- but it wasn't. Not only did the race set up perfectly for Charleston Rag -- two speed horses went head and head and then collapsed -- but her winning time of 1:39 for a mile was ridiculously slow. An average field of $10,000 claimers would run that fast. If this were even a fair-to-middling crop of 2-year-old fillies, Charleston Rag would be getting trounced by a dozen lengths.

But none of her rivals in the Selima has particularly solid credentials, either. A case can be made for Mom's Command, who has had trouble coming out of the gate in each of her last three starts. Now she gets a jockey change from Abigail Fuller to Gregg McCarron, which should enhance her chances. Sociable Duck finished second in Saratoga's Spinaway Stakes, and she could be a serious factor, too, although she has been laid off for two months and is attempting to go 1 1/6 miles for the first time. Golden Silence, who won a prep race at Laurel last Saturday, also has a shot. It's a tough race to handicap, but this much is certain: The winner is unlikely to go on to be regarded as one of the immortals of the American turf. Unfortunately, there is no way to bet on that proposition.