Richard Dutrow Jr., the controversial trainer of Kentucky Derby and Preakness champion Big Brown, spent much of the summer firing verbal jabs at Curlin. He is not about to stop, not after his rival finished a disappointing fourth in the $5 million Breeders’ Cup Classic on Saturday, to raise questions about his legacy and whether he can repeat as Horse of the Year.

As Dutrow sees it, strong arguments can be made for Big Brown, Curlin and unbeaten filly Zenyatta when the time comes to vote for Horse of the Year. “I think we have as good a chance as those two,” he said.

Jess Jackson, Curlin’s owner, contends that his 4-year-old had nothing left to prove, even in his bid to repeat in the Classic. “He’s already a champion,” he said. “I don’t think this loss diminishes his chance to be Horse of the Year at all.

“Big Brown ought to be the top 3-year-old, but we went to every race, and that’s the spirit of the sport.”

Injury-plagued Big Brown, eased in the Belmont Stakes in a failed bid for the Triple Crown that devastated racing fans, was retired after he was hurt in a workout a few weeks ago before his eagerly anticipated showdown with Curlin at the 25th Breeders’ Cup.

When trainer John Shirreffs was asked if there is a case to be made for his filly Zenyatta, his response could not have been more emphatic: “Absolutely. With her being undefeated in three Grade I’s before the Ladies’ Classic, she’s really proven herself.”

Zenyatta improved to 7-for-7 this season with a dazzling last-to-first move Friday in the Ladies’ Classic. She is unbeaten in nine career starts, with all but one of those successes occurring on a synthetic surface.

The tall and imposing Zenyatta can count ex-jockey Gary Stevens among her fans. “She could win on broken glass, it doesn’t matter,” he said.

Curlin’s ability to respond to his first test on Pro-Ride was a question leading up to the Classic. Jackson debated long and hard whether to run. He insisted afterward that he was not making excuses for a loss but said, “This track was for turf runners or runners who had been on it before.”

Curlin’s only blemish in six previous starts this season was a runner-up finish to Red Rocks in his only turf try at Belmont Park in July.

He traveled halfway around the world and routed his competition by 7¾ lengths in the $6 million Dubai World Cup at the end of March, then held his form when he rolled by 4¼ lengths in the Stephen Foster Handicap at Churchill Downs in mid-June. He earned consecutive wins in the Woodward and the Jockey Club Gold Cup to become the first North American horse to roll into the $10 million dollar club.