There in the morning fog, with the grandstands of Churchill Downs floating throuh the faraway mist, an old buddy called over to Herb Stevens, "How's the blood pressure?"

Stevens quickly clasped a hand over his right wrist, as if taking his pulse. "Went to the doctor t'other day," the horse trainer said. "Told me I was like a 19-year-old. Damn machine must be broke."

Herb Stevens is 63. He trains Rockhill Native, the likely favorite in Saturday's 106th Kentucky Derby. He is a wonderful curmudgeon in cowboy boots, loose leather gloves and a practical scowl. Jack Klugman, the TV star, is the hot story here. Herb Stevens the hillbilly hardboot, is the heart story. For 12 years, Klugman has had a horse. Herb Stevens started during the war. The Civil War.

The racing line of the Stevens family in Kentucky runs to the Civil War when Herb Stevens' great-grandfather, John; occasionally moseyed into a little town with pair of quarter horses. He had one horse pulling the buggy, the other loping along easily tied to the back. Shortly before arriving in a new town, he would switch the horses, hooking up the fresh one to pull the load.

Well, don't you know Kentuckians? Soon as Stevens got into a new town, he would hear about the fastest horse around. John Stevens would argue until he couldn't take it anymore, whereupon announcing, "Hell, I got a buggy horse that can beat that horse."

If there's one thing a Kentuckian knows, it's a sure thing. And surely the town's fastest horse could beat a nag that had been pulling a buggy across country. So the townfolk would whip out some money and say put up or shut up. John Stevens would agree, reluctantly of course, to put his son on top of the buggy horse.

Amazing, everyone agreed, how fresh that buggy horse looked as he left the local hero back over the hill.

John's son, Thomas, later trained the winner of the 1887 Kentucky Oaks, a filly classic, and sent an also-ran in the 1903 Kentucky Derby, then a race that didn't mean much. Thomas' son, James, trained horses for 55 years without getting into the Derby, which in his last year was a very important race. And now comes James' son, Herb, who saw his first Derby at his father's side in 1934, who has trained hundreds of goats masquerading as horses, who has stayed away from Churchill Downs on Derby Day because his lame and halt didn't belong in the world's greatest horse race; now comes Herb Stevens, the great-grandson of a buggy hustler, about to win the Derby.

"One more night of no sleepin,' "I'll be sleepin' standin' up during the Derby," he said this morning. He stood on the red loam of the backstretch. It is his place. The smells are his, the leather and liniment and manure. His horse was on the track for this morning constitutional, a leisurely gallop of two miles, and Herb Stevens watched Rockhill Native with eyelids narrowed and unblinking a diamond cutter's laser glare.

"I slept good 'til 3 a.m.," he said, still watching his horse but joking with newspapermen all the while, "when my night watchman called and I had to go foal a mare. By time we finished up, it was too late to go back to bed. Hell, I fell asleep in the barber chair Thursday."

It's not nerves keeping Stevens up. He's just running out of hours in the day. He has a 260-acre breeding farm outside Versailles, Ky., 60 miles from here, and his stable of runners is at Keeneland Race Course, 20 miles from his home. He has those chores to attend to, in addition to coming to Churchill Downs to work with Rockhill Native, the horse of hardboot's 3 a.m. dreams.

Cheap leather kept in mud for a decade or two turns very hard. Cheap boots get hard. Hardboots. Hardboots are horsemen who have scuffled for a quarter," said Herb Stevens, whose spread today is worth 5,000 an acre ($1.3 million). With cheap horses at bush-league tracks, Stevens has done passingly well.

"This is your chance," the old buddy said to Stevens there in the morning mist.

"Been a long time gettin' here," Stevens said. His floppy hat dips near the top of heavy black-rimmed eyeglasses. You yet could see the fun in his eyes. They fought the Civil War when this thing started. "If it's this long to the next 'un, I won't be here," Stevens said.

Lots of times Stevens could have run a horse in the Derby, but he chose not to. He said, trying to explain why a Kentuckian would steer clear of the Derby, that it was a matter of principle. The principle was that Churchill Downs didn't provide enough seats for horsemen. Among other things, Herb Stevens is a stubborn cuss of a hardboot.

"I told the ol' racin' secretary here that I wasn't comin' here until they gave us someplace to sit down and watch the Derby from," Stevens said.

Then he added the real reason.

"I told him I wasn't comin' to the Derby unless I had a horse 5 to 1 or less."

As the trainer spoke, Rockhill Native was 8 to 5 to win the Derby. Winner of 10 of 15 races, including the essential Blue Grass Stakes at Keeneland 10 days before the Derby, "Rocky," as Stevens calls him, is knocked only for being too small, a 900-pounder who would need a ladder to look Secretariat in the eye."If size meant anything," Stevens said, "a cow would outrun a rabbit."

Stevens sometimes speaks gruffly, the words ground out between his back molars, popping into the air dressed in barbed wire. He was seated at the dais for a banquet early this week; his wife was put at a table in the back of the room. Stevens turned loose.

"By God, she's been good enough to sit with me for 37 years," he said. "She's good enough to sit with me tonight."

Stevens' dinner companion, Sande Stone, wife of the Churchill Downs' president, sought to soothe the fractious trainer.

"The steak is good," she said sweetly.

"Too damn much garlic," Stevens said.

"Green beans . . ." Mrs. Stone started.

"Came out of a damned can," Stevens said.

That night, Mrs. Stone came down with hives.