(Reuters) - Beholder, the 3-1 second choice on the morning line behind favourite American Pharoah for Saturday's Breeders' Cup Classic, has been withdrawn from the showpiece race due to health concerns.
The 5-year-old mare, winner of the Breeders' Cup Juvenile Fillies in 2012 and Distaff in 2013, was discovered to have bled after her morning gallop on Thursday in Lexington, Kentucky.
"There's obviously some irritated lung tissue there," Beholder's trainer Richard Mandella said in a statement. "She will be fine, but if I put her under the pressure of a race situation, it could cause some real damage.
"After she galloped this morning we scoped her and found her to have bled. This was obviously due to the fever she had when she arrived. Knowing this, we feel it is too great a risk to start her in the Classic."
The twice Eclipse Award champion, with Hall of Fame jockey Gary Stevens on board, had been scheduled to start the $5 million Classic from the 10 hole as a 3-1 early choice.
The mare has won all of her five starts this season, including the Pacific Classic at Del Mar against male rivals over the Classic distance.
In Beholder's absence, the heavily fancied American Pharoah looks an even likelier bet to end his stellar Triple Crown career with a win in his hugely anticipated farewell at the Keeneland Race Course in Lexington.
The Bob Baffert-trained 3-year-old, aiming for a ninth win in 11 lifetime starts, had been installed as the early 6-5 favourite earlier this week but that was revised to 4-5 on Thursday following Beholder's withdrawal.
American Pharoah will break from the fourth post on Saturday in a nine-runner field.
Tonalist, the 4-year-old who dashed California Chrome's Triple Crown bid in 2014 with a thrilling victory at the Belmont Stakes, is the second choice at 4-1 with exciting stretch-runner Honor Code at 5-1.
American Pharoah entered the pantheon of U.S. thoroughbred racing's all-time greats by winning the Belmont Stakes wire-to-wire in June to become the first horse to capture the coveted 'Triple Crown' in nearly four decades.
In winning a seventh straight race, American Pharoah became the 12th horse and first since Affirmed in 1978 to sweep the Kentucky Derby, Preakness Stakes and Belmont Stakes.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)