The improbability of the back stories that brought Mucho Macho Man into the stretch as the front-runner in Saturday’s $5 million Breeders’ Cup Classic would have knocked the bay horse off stride were he capable of being aware of such things.

Even Hall of Fame athletes aren’t supposed to return from seven-year retirements and achieve wins they never previously experienced. And never mind that the trainer who had babied her 5-year-old horse through various problems wasn’t sure five years ago she’d live to see her kids grow up, much less celebrate her first Breeders’ Cup win.

It was all too much to fathom. And after a photo finish of impossibly close proportions, all the above rang true before 58,795 at Santa Anita Park.

The career comeback of Hall of Fame jockey Gary Stevens and fight for her life Kathy Ritvo successfully engaged in 2008 both hit pinnacles when Mucho Macho Man, owned by Dean and Patty Reeves of Suwanee, got his nose down a hair ahead of Travers Stakes winner Will Take Charge to win the 11/4-mile Breeders’ Cup Classic.

The 29 prior editions of the Classic have seen some finishes for the ages, but the enormity of Mucho Macho Man’s holding on after opening up a 1-length advantage in the lane deserves its own category.

Stevens, who won the Breeders’ Cup Distaff on Beholder on Friday, ended his seven-year retirement from riding last January and now has the Breeders’ Cup Classic win that was missing from his résumé. His fortitude is matched only by Ritvo, who underwent a heart transplant in 2008 after suffering from cardiomyopathy,

“It’s actually the culmination of a career. I had never won a Breeders’ Cup Classic,” said Stevens, who rode Mucho Macho Man for the first time when the son of Macho Uno won the Grade I Awesome Again Stakes over the same Santa Anita track on Sept. 28. “I’d been so close so many times and I figured it just wasn’t meant to be.

“We had talked about this in the past five weeks that maybe this was meant to be because I’m sure enjoying this more than any victory. I can’t believe that it happened.”

Having finished second to Fort Larned in the 2012 Classic, Mucho Macho Man was expected to be among the leaders of the handicap division this season. Hardships fell upon him though when he began his 2013 campaign by being pulled up in the Sunshine Millions Classic. He was later found to have a bacterial infection and then a quarter crack that kept him out of the Grade I Met Mile.

Following third-place runs in the Criminal Type Stakes and Grade I Whitney, Mucho Macho Man earned the first Grade I win of his now 23-race career when he took the Awesome Again by 41/4 lengths.

“This thing has really been a team effort,” Reeves said. “He gives you everything he’s got every time out.”

It took everything Mucho Macho Man had in him to hold off the big white face of Will Take Charge and the bay legs of multiple Group I winner Declaration of War making his first stateside start.

Away sharply out of post No. 6, Stevens kept Mucho Macho Man tracking in a clear outside path fourth then fifth as Fort Larned faced prompting from Moreno and a hard-luck Game On Dude through fractions of :23.39 and :46.36.

When race favorite Game On Dude — who was in the Classic for a third straight year — came to Fort Larned approaching the final turn, Mucho Macho Man moved right with him and then past the seven-time Grade I winner to take command of the 11-horse field.

“When Gary came to me, I squeezed him a little to put some distance between us and I couldn’t,” said Mike Smith, jockey of Game On Dude. “I knew I was in trouble.”

Will Take Charge meanwhile was making his rally, coming extremely wide around the turn with Palace Malice carrying him out. Will Take Charge caught Declaration of War moving ahead of him and was half a stride away from his own Classic glory as they hit the wire in 2:00.72.

“It’s just a heartbreak that he lost. He did everything right,” said Hall of Famer D. Wayne Lukas, trainer of Will Take Charge.

Game On Dude finished ninth, likely ending his Horse of the Year hopes, with defending race winner Fort Larned fourth in his final career start.

Where Mucho Macho Man fits into year-end honors remains to be seen, not that a trophy could match the joy he has already produced.

“It’s been an amazing, amazing trip,” Ritvo said. “I still don’t even know how to feel.”