Preakness winner Rachel Alexandra will not run in the Belmont Stakes, opening the way for jockey Calvin Borel to return to Kentucky Derby winner Mine That Bird in his quest for a personal Triple Crown.

Jess Jackson, Rachel Alexandra's co-owner, said yesterday 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."

AUTO RACING

REUTIMANN ON A ROLE

David Reutimann played the Sprint Cup waiting game and again came out on top.

Reutimann ran a lap of 156.794 mph yesterday and captured the pole for tomorrow's Autism Speaks 400 at Dover International Speedway in Delaware, four days after he won his first career Sprint Cup race.

The victory in the Coca-Cola 600 came after three rain delays at Lowe's Motor Speedway. Reutimann then went out 11th yesterday and watched other drivers take a shot on the concrete track at trying to knock him off the pole.

Kasey Kahne was second and Juan Pablo Montoya qualified third.

BOXING

WBA TITLE MATCH OFF

Ruslan Chagaev failed a "medical requirement" yesterday, forcing his challenge for Nikolai Valuev's WBA heavyweight title to be called off a day before the fight in Helsinki.

Finnish officials said "Chagaev has been unable to fulfill the Finnish Boxing Federation's medical requirements" but gave no further details.

It's the third time their rematch has been canceled since Chagaev (27-0-1, 26 KOs) gave the 7-foot Russian (50-1-0, 34 KOs) his only pro defeat in April 2007. The previous two rematches were called off because Chagaev ruptured an Achilles' tendon in training.

COLLEGE BASKETBALL

CALIPARI NOT 'AT RISK'

A letter from the NCAA tells new Kentucky coach John Calipari he must participate in next week's hearing on alleged major violations at Memphis, even though he isn't considered "at risk" in the probe.

Calipari, who coached the Memphis Tigers during the 2007-08 season in question, will be in China and will participate in next Saturday's hearing in Indianapolis by phone.

"I am very willing to cooperate with the committee and provide my views on the issues involved in this case," Calipari said