ESPN Horse Racing

BALTIMORE -- Calvin Borel and tension go together about as naturally as grits and champagne. He's simply not the nervous, brooding, introspective type.

In fact, there are times when you see his vacant grin in the post parade minutes before a big race and wonder whether he's thinking about what to eat for dinner.

But even the naturally sunny, supremely unserious Cajun jockey has to feel a little weight on his shoulders this week. He'll be doing the unprecedented Saturday in the Preakness, and anything less than victory will lead to relentless second-guessing of the little man.

In the previous 133 runnings of the Preakness, the winning jockey in the Kentucky Derby has never given up riding his Derby mount in favor of a different horse in the second leg of the Triple Crown. There have been times when the Derby winner has not run in the Preakness, but never has a jockey flat-out jilted the horse than won the roses to compete against that horse on someone else.

Borel did that. Not only did he drop Derby winner Mine That Bird after a daring ride that all but cemented his Hall of Fame credentials, he dropped him for a filly. And fillies win Triple Crown races about as often as the Toronto Raptors make the playoffs.

Of course, Borel's mount is not just any filly. She is Rachel Alexandra, the filly Borel has ridden to five straight victories, most recently a dominating, 20¼-length victory in the Kentucky Oaks. The best filly anyone has seen in decades. Some suggest the best since Winning Colors won the Kentucky Derby in 1988, others say the best since ill-fated Ruffian in 1975.

Borel isn't into historical comparisons. He only knows she's the best racehorse he's ever sat on, and this is a guy who has won two of the past three Derbies.

That's why he just about guaranteed victory Friday morning in a conference call from his home in Louisville with reporters here.

"[Mine That Bird] will have to run the race of his life to beat my filly," Borel said. "I think all [12] other horses will have to run the race of their life. Or I'll have to fall off."

Borel is so uptight about this Preakness that when reporters called his house, his fiancée, Lisa Funk, had to go outside and get him.

"He's mowing the yard," she said.

Classic Calvin. Still, the unhurried and unworried jock knows what is riding on his decision.

"I've got a lot to prove to the people and the public to show she's the best horse in the race," he said.

So that's why he made the switch, despite some second -guessers who say you should never abandon a chance at the rarest of all racing accomplishments, a Triple Crown.

But honestly, Mine That Bird is no Triple Crown horse. Borel and just about everyone else in racing strongly suspect that. It's why Rachel Alexandra is the 8-5 favorite in the Preakness and Mine That Bird is the 6-1 co-third choice.

And it's why Borel said from the get-go -- less than an hour after winning the Derby -- that if they ever ran in the same race, he'd choose Rachel over the Bird in a heartbeat.

He's been consistent with that, which is why Mine That Bird's camp of cowboys bears no ill will toward Borel.

"This is a business and Calvin has to look out for himself," said Mine That Bird trainer Chip Woolley, who named 2005 Kentucky Derby winner Mike Smith as his new jock. "It was a hard choice to make, and I appreciate the fact that him and his agent [Jerry Hissam] were up front with us while making their decision. We'd love to have him on our horse, but that's part of the business."

Still, it's a weird part of the business. Horses simply don't change ownership and barns between legs of the Triple Crown, as Rachel Alexandra did when she was sold from Dolphus Morrison to Jess Jackson for somewhere in the fat seven figures.

That moved her from a man staunchly against running fillies with colts to a man who couldn't wait to run her on this big stage in Baltimore. And that left Borel nervous … very nervous. He thought Jackson and new trainer Steve Asmussen might look for another rider for Rachel.

"I watched her walk away [from Hal Wiggins' barn] with tears coming out of my eyes," Borel said.

But Jackson told him shortly thereafter, "She's yours as long as you want her." Borel definitely wanted her in this race.

"Like I said all along, I think she's the best horse in the world," Borel said. "And I'm not going back on my word."

She will, however, require a vastly different ride than the one that won Borel both of his Derbies.

With both Street Sense in 2007 and Mine That Bird, Borel dropped to the back of the pack and saved ground, hugging the rail. That's the trademark Borel ride, and it was necessary to produce that staggering Derby upset two weeks ago.

"He's the only one who could have won on that horse," said trainer Bob Baffert, who saddled runner-up Pioneerof The Nile. "He rode to get a piece of the pie and he got the whole pie. He got my pie.

"I was joking that Calvin should get the purse and give the owners 10 percent [the opposite of the usual arrangement]. It was a brilliant ride."

On Saturday, Borel and Rachel will start as far away from the rail as possible, drawing the No. 13 post in a field of 13. And he will have to use Rachel's tactical speed to gain position near the lead heading into the first turn.

From there, he will have to judiciously judge the pace and try to keep Rachel from doing what she's done every time he's ridden her: clicking off the first half-mile in roughly 47 seconds, the first three-quarters in 1:12, and then steadily pulling away with her mesmerizing stride.

"She has the most unbelievable stride you've ever seen in the world," Borel gushed.

If Rachel Alexandra has the lead in the stretch, Borel is absolutely certain he'll win. But you can also be certain he'll keep his eyes wide open for one horse surging late: Mine That Bird.

"If we can't win it, I hope they do," Borel said. "… If they win, I promise I'll be the first one there to congratulate them."

Then he'd have to face the second-guessers.

Only one result will keep them quiet and justify Calvin Borel's unprecedented decision. A win.

Pat Forde is a senior writer for ESPN.com