Louisville, Ky. ? Calvin Borel was in a familiar place, along the rail and urging Mine That Bird to fly through the mud. Trainer Bennie Woolley Jr. was someplace he never imagined — the Kentucky Derby, with his horse in the lead.

Together, they pulled off one of the greatest upsets in 135 years of America’s most famous horse race.

“It was a Street Sense move,” Borel said Saturday, referring to the same rail-hugging ride he gave that colt to win the Derby two years ago. “They can only go so fast, so far. When I hollered at him, he just went on.”

Sent off at 50-1 odds, Mine That Bird pulled away in the stretch to score a 63/4-length victory at Churchill Downs, the second-biggest upset in Derby history. His margin was the largest since Assault won by eight lengths in 1946.

The gelding ran 11/4 miles on a sloppy dirt track in 2:02.66 and paid $103.20 to win — second-largest payout in Derby history behind Donerail ($184.90) in 1913.

Pioneerof the Nile finished second for freshly minted Hall of Fame trainer Bob Baffert, a three-time Derby winner. Musket Man was another nose back in third, followed by Papa Clem.

Friesan Fire, the 7-2 wagering favorite of 153,563 fans, was 18th in the 19-horse field.

Earlier, I Want Revenge became the first morning-line favorite to be scratched on Derby Day after inflammation was detected in the colt’s left front ankle. The injury wasn’t believed to be career-threatening but worrisome enough to prompt trainer Jeff Mullins and owner David Lanzman to withdraw.

Mine That Bird got squeezed coming out of the starting gate, but Borel took a firm hold and wrestled the horse to the rail while they were in last place.

They were 12th and going strong with a quarter mile to go, after working their way around Atomic Rain. Borel quickly angled Mine That Bird back to the inside with three-sixteenths to go and shot the gelding through a tight spot approaching the eighth pole.

“I had enough room,” Borel said. “He’s a small horse.”

Once free, Mine That Bird quickly accelerated toward an improbable victory.

“I salute Calvin for his terrific ride,” trainer Todd Pletcher said.