Jess Jackson, Rachel Alexandra's co-owner, said Friday the spectacular filly "deserves a well-earned vacation."
Rachel Alexandra, the first filly to win the Preakness in 85 years, had been set to work out Monday at Churchill Downs in Louisville, and no announcement was expected until after that. But Jackson explained she simply needed a rest after running - and winning - four graded stakes races since March 14, including a dominating victory in the Kentucky Oaks.
"We know the media and many fans would have liked to see her run in the Belmont Stakes - we feel the same," Jackson said in a statement. "But all of us sincerely interested in the horse must agree that we only want to see her run when it is best for her. While she is in great shape, having strong works, and recovering well from her amazing performances, we feel Rachel deserves a well-earned vacation."
Borel was the jockey aboard for both Mine That Bird in the Derby and Rachel Alexandra in the Preakness and Oaks. He was set to ride her again in the Belmont, but Mine That Bird's trainer Chip Woolley had said he was prepared to wait - even into next week - if there was a chance Borel could become available again.
"We hate she's not going to be in there for horse racing, but at the same time it's maybe better for me," Woolley said Friday in a phone interview. "It was a very strange year where you had two great horses and the same guy riding both of them."
Borel, who was riding in nine races on Friday's card at Churchill Downs, was already planning to be aboard Mine That Bird on Monday at the Louisville track for the colt's final workout before shipping to New York for the Belmont.
In a statement from the New York Racing Association, Borel thanked Woolley and Mine That Bird's owners "for being so gracious and allowing us to wait for this decision." Borel also praised Jackson for making the announcement earlier than expected.
"Now that the decision is made, I am excited to come to New York and ride Mine That Bird in the Belmont Stakes," Borel said.
There was no immediate indication from Jackson on when or where Rachel Alexandra might race next, but the New York Racing Association said he had committed to a start at Belmont Park sometime this year.
The filly had become a popular favorite since her stretch of big wins, even posing Friday morning for a photo spread in Vogue magazine.
Borel, who had won the Derby two years earlier aboard Street Sense, repeated the feat with Mine That Bird, even though at 50-1 he was one of the biggest long shots ever to win the most famous American horse race.
The horse nearly pulled off another win in the Preakness with new jockey Mike Smith aboard, finishing second to Borel and Rachel Alexandra.
Among the possible challengers to Mine That Bird in the third leg of the Triple Crown is Summer Bird, who shares the same sire - Birdstone, who foiled Smarty Jones' Triple Crown attempt by winning the 2004 Belmont. Also expected to run are Chocolate Candy, Dunkirk, Flying Private, Brave Victory, Charitable Man, Luv Gov, Miner's Escape, Mr. Hot Stuff and Nowhere To Hide.