Calvin Borel rides Mine That Bird to victory in the 135th Kentucky Derby horse race at Churchill Downs on Saturday, one of the biggest upsets in the event's history. (Rob Carr/Associated Press)

Mine That Bird, the top two-year-old in Canada for 2008, was a huge upset winner in the 135th running of the Kentucky Derby on Saturday afternoon.

The horse exploded over the final two furlongs, racing down the rail to win after going off at 50-1 in the first leg of U.S. thoroughbred racing's fabled Triple Crown.

It was the second-biggest upset in Derby history, behind 1913's Donerail, and it sent the Churchill Downs crowd — especially those who had bet on the Kentucky-bred gelding — into a frenzy.

Last into the first turn after getting squeezed out of the gate, jockey Calvin Borel brought Mine That Bird off the final bend in 14th, saw a hole inside and took off at the 16th pole in an amazing sprint to the line for a 6¾-length victory.

Pioneer of the Nile, trained by three-time winner Bob Baffert, finished second, with Musket Man third in the Louisville event.

The winning time was a not-surprisingly slow 2:02.66 on a rapidly drying track that had taken a lot of overnight and morning rain.

Now trained by Chip Woolley Jr., Mine That Bird ran twice as a three-year-old, finishing fourth and second in relative anonymity at Sunland Park in New Mexico.

Great year at Woodbine

He was almost unbeatable as a two-year-old at Toronto's Woodbine Racetrack, winning four times in five races. But when he went to the Breeders' Cup Juvenile last fall, Mine That Bird was a dismal 12th.

The gelding, who paid $103.20 US to win, $54 to place and $25.80 to show, was bred by Toronto's Peter Lamantia and American partners Needham/Betz Thoroughbreds and James Blackburn.

He was once purchased by Canadian trainer-owner Dave Cotey for $9,500 US.

After winning the Grey Stakes at Woodbine last Oct. 5, he was sold to Double Eagle Ranch and Bueno Suerte Equine for an undisclosed sum. Training duties switched to Woolley.

Cotey was thrilled by the finish.

"I am so happy for him. I'm ecstatic. I'd love to be down there to give him a big kiss."

He'd have to get in line. After the run out, jockey Borel brought Mine That Bird back in front of the grandstand instead of going straight to the winner's circle.

The crowd loved it and showered the mud-speckled horse with applause in a scene reminiscent of the film Seabiscuit.

"Calvin did a super job," Woolley said. "I just can't say enough about the way things went for us. Calvin picks a spot, everything fell together. We were really lucky to get through there."

Borel, whose love of the inside has tagged him with the nickname "Bo-Rail" won the Derby two years ago with Street Sense. This time around the mile and a quarter, he stuck to his plan.

"You got a hole, you got a shot," he said afterward, admitting the hole was rather small.

"He had enough room," Borel laughed. "He's a small horse."

Mine That Bird is the ninth gelding to win the Derby and just the second in the last 80 after Funny Cide in 2003.

That horse is now the personal mount of famed trainer Barclay Tagg, who saddled Canada's Tale of Ekati to a fourth-place finish at last year's Derby.

Bloodlines strong

While this year's Derby winner may be unknown to American bettors, his bloodlines are first-class.

By Birdstone, winner of the 2004 Belmont Stakes, and out of Mining My Own, Mine That Bird is a grandson of the great Canadian breeding stallion Smart Strike, who coming into this season had sired 56 stakes winners.

On his dam's side there's also Mr. Prospector, Classy and Smart and Vice Regent. His sire's background includes Unbridled, the 1990 Kentucky Derby and Breeder's Classic winner, and Storm Bird.

On both sides is great-great grandfather Northern Dancer, the 1964 Kentucky Derby and Preakness winner from Canada, the top sire of all time and himself a small horse.

Smart Strike's influence on the 2009 Derby went even deeper as he also sired fourth-place finisher Papa Clem.

With files from The Canadian Press