There will be a race within a race at Churchill Downs on Saturday: the battle between Eternal Prince and Spend A Buck for the early lead in the Kentucky Derby. As in thermonuclear war, all the combatants are likely to wind up as losers.

Both colts are brilliantly fast, and both have run their best races when they can open a clear early lead. Neither has run so well when subjected to head-and-head pressure. If one of the horses were permitted by the other to take an uncontested lead, he would be formidable, and so the two camps have already started playing a game of brinksmanship.

"We'll have the lead," Eternal Prince's trainer Butch Lenzini said this morning, "unless Spend A Buck wants to go real fast and make the pace suicidal for both of us."

Lenzini understands the importance of speed better than most horsemen. Many trainers cling to the myth that the way to get a speed horse to go a distance is to restrain him early and conserve his energy. That almost never works.

The way to win with a speed horse is to let him roll early, open a clear lead, then get him to relax and slow down as he controls the pace. That's how Lenzini won the Preakness with Aloma's Ruler, and that's how he scored the successes with Eternal Prince that brought him to Churchill Downs.

The trainer learned his lessons about Eternal Prince last month, when he sent the colt into Aqueduct's Bay Shore Stakes against another speedball. He told jockey Richard Migliore to sit second behind the front-runner.

"I thought he'd be able to take back, but Richard really had to fight the horse." Eternal Prince ran dismally. But when Migliore let him roll in his next two starts, Eternal Prince led all the way to win the Gotham and Wood Memorial Stakes, establishing himself as a legitimate Derby contender. He looked so good that New York Yankee owner George Steinbrenner paid $1 million for a 37.5 percent share of the colt.

While Eternal Prince's victories were very impressive, Spend A Buck's front-running triumph in the Garden State Stakes was incredible. Even trainer Cam Gambolati said, "I never thought in my wildest dreams that he could run that good."

After taking the early lead without a challenge, Spend A Buck ran 1 1/8 miles in 1:45 4/5, two-fifths of a second off Secretariat's world record. The track was very fast, leading some people to underestimate the significance of the time, but this was nevertheless a superhorse performance.

Spend A Buck has at least as much raw ability as Chief's Crown, the Derby favorite -- but he doesn't have the versatility. He seems to need the early lead to do his best.

So what will his strategy be on Saturday? Gambolati said he won't give his jockey, Angel Cordero Jr., any instructions, but he said, "I assume Angel will try to sit second."

Maybe, but there are few riders who love to use their horses' speed more than Cordero. Lenzini understands the jockey's tendencies. "Cordero makes it a little tough," he conceded. "He's not going to let you steal anything. He's tough in a one-on-one situation."

The situation looks impossible for both colts. After they battle with each other in the early stages of the Derby, they will have to cope with the challenges of Chief's Crown and Rhoman Rule, both of whom will be stalking them and figure to make their moves in mid-race.

If one of the speed horses should survive to this point, he would then have to withstand the late moves of stretch-runners like Proud Truth and Stephan's Odyssey. It's too much to ask, even for horses with the talent of Eternal Prince and Spend A Buck.

Lenzini understands the situation well, and instead of worrying about Chief's Crown or any of the other contenders, he said, "If Spend A Buck was out of there, I'd be pretty happy."

That's the answer! Since Steinbrenner is not reluctant to spend his money for athletes, he ought to buy Spend A Buck. He could probably get the colt for one-third of what he paid for Dave Winfield, and he wouldn't have to worry about the horse talking back. Then he could put one member of his equine team on the bench Saturday, and let the other one try to lead the Kentucky Derby from start to finish.