(Reuters) - Justify, the undefeated winner of U.S. thoroughbred racing’s coveted Triple Crown this year, has been retired from racing, his connections announced on Wednesday.

Slideshow ( 3 images )

The 3-year-old son of Scat Daddy won all of his six career starts, most notably the Kentucky Derby, Preakness Stakes and Belmont Stakes to become only the second Triple Crown winner since 1978.

“Justify had some filling in his ankle, and he is just not responding quick enough for a fall campaign,” said Hall of Fame trainer Bob Baffert. “We all wanted to see Justify run again, but ultimately it is my responsibility to make sure he is perfect. Without 60-90 days, I can’t be definite.”

Justify broke the “Curse of Apollo” in May when he triumphed at the Kentucky Derby, the first leg of the Triple Crown, to become the first horse since Apollo in 1882 to win the Run for the Roses without starting as a 2-year-old.

From there, Justify, ridden by Mike Smith, never looked back as he fended off all challengers to record a wire-to-wire victory at a foggy Preakness Stakes before winning the Belmont Stakes by 1-3/4 lengths.

“Like everyone else, I am disappointed he won’t run again, but I am thankful he came into my life,” said Hall of Fame rider Smith.

“There was never a time when I rode him that I felt like I was going to get beat. There was no horse who could run with him without sacrificing themselves, and there was no horse who could come get him. He truly is a gift from God.”

Campaigned by WinStar Farm, China Horse Club, Head of Plains Partners LLC, and Starlight Racing, Justify was purchased for $500,000 in 2016 and went on to amass earnings of $3.8 million.

“The timing is bad for another start in 2018, and therefore, we have to retire him,” said WinStar Farm’s Elliott Walden.

“We can’t take the risk of running Justify as a 4-year-old. We all wanted him to finish his career in the Breeders’ Cup Classic (in November), but it was not meant to be.”

Walden also said there is a possible sale of Justify, who will parade at Del Mar racetrack in California on Saturday, in place that a deal will not be finalised until a later date.