As a devout believer in the significance of speed, I was both surprised and dazzled by the performance of Chief's Crown in the Blue Grass Stakes in Lexington, Ky., last week.

The colt had never impressed me before, but when he ran 1 1/8 miles in a near-record 1:47 3/5, with the last eighth of a mile in a phenomenal :11 4/5, his brilliance was evident.

Like just about everybody else who saw that race, I left Keeneland thinking that Chief's Crown was a standout to win the Kentucky Derby. But something about the Blue Grass kept gnawing at my mind, until I woke up in the middle of the night with a flash of insight: That supposedly brilliant performance was an illusion.

It was a phony.

Chief's Crown has plenty of virtues -- his consistency, his versatility -- but he still has not given a blockbuster performance as a 3-year-old.

Even for racing people who aren't normally time-conscious, the 1:47 3/5 clocking was the persuasive part of Chief's Crown's performance. After all, he was facing three ineffectual rivals, and he was permitted to take the early lead without a challenge. Under the circumstances, he couldn't lose.

Indeed, there are probably a dozen other 3-year-olds who would be expected to blow away the same field if they were presented the same circumstances.

After judging the speed of the Keeneland track, I guessed that Chief's Crown would run in 1:49 1/5 if he duplicated the best previous performance of his career. If his rivals also repeated their best route races, he figured to beat Banner Bob by five lengths and Floating Reserve by about seven.

Chief's Crown scored by 5 1/2 lengths over those two colts, which made perfect sense, but the time didn't. Not only did Chief's Crown run 1 3/5 seconds better than his lifetime best race, but so did both the horses behind him, which seems an implausible coincidence.

In the case of Banner Bob, I find it inconceivable. This winter he was in razor-sharp condition when he came into the Florida Derby, which was run on a Gulfstream Park track only about a fifth of a second slower than Keeneland's.

With no credible speed in the field to press him, the spot was ideal for him. Banner Bob proved conclusively that he wasn't a 1 1/8-mile horse, when he faded badly in the stretch. He finished the race in 1:50 3/5, with the last furlong in a slow :13 3/5.

Yet at Keeneland, if the time is to be believed, Banner Bob went the distance in 1:48 4/5 with the last eighth in :12 2/5. That is a sterling performance, far superior to the victories of Spectacular Bid, Alydar and Riva Ridge in the Blue Grass.

Is the faint-hearted Banner Bob really capable of such a race? No way. Nor is Floating Reserve, who finished out of the money three straight times against a weak California bunch of 3-year-olds but was credited with a 1:48 4/5 time and a :12 flat last furlong at Keeneland.

If their figures are spurious, then those of Chief's Crown are, too. But how? Why?

Speed handicappers who deal regularly with the nuances of horse-race times know that such impossible times do occasionally occur. An entire field will run dramatically faster or slower than it is supposed to and, when the horses run again, they will revert to their usual level of performance, verifying that the implausible time was indeed a phony.

This may happen because of something the maintenance crew did to the track before the race, because of a change in the weather, because of a malfunction in the timer. A couple of these explanations are possible in the Blue Grass.

Keeneland uses the unreliable Visumatic Timer -- the same system which deprived Secretariat of his rightful track record in the Preakness, and which credited Althea with an :11 2/5 final furlong in last year's Arkansas Derby before she came to Churchill Downs and finished 19th.

One professional clocker found a two-fifths of a second disparity with the "official" time of the Blue Grass. Moreover, the track may have been souped-up for the stake, because the time of the last race on the Keeneland card seemed extraordinarily fast, too.

So what really happened in the Blue Grass Stakes? I believe that Chief's Crown ran his usual race, workmanlike but not very fast, to beat a couple of rivals who ran their usual mediocre race.

Any good speed horse in the field for the upcoming Derby -- Spend A Buck, Eternal Prince, Rhoman Rule -- would have looked at least as good under the same circumstances. This is not to say that Chief's Crown is a bum with no chance to win Saturday, but he has no edge over his rivals and he will have to run a much-improved race to win.

Unfortunately, there is no way to test my thesis before the Derby is run. If Chief's Crown wins by five lengths in 2:00 or thereabouts, and Floating Reserve also runs a very strong race, then the time of the Blue Grass will be verified. But it is far more likely that Chief's Crown is being greatly overrated because of what he did last Thursday and he will be a vulnerable favorite in the Derby.