Accelerate has all but assured his place as North America's best older horse with his win in the Breeders' Cup Classic at Churchill Downs in Kentucky.

The John Sadler-trained five-year-old took the lead at the top of the straight and held off Gunnevera to win the $6 million Classic by a length, strengthening his bid for Horse of the Year honours over Triple Crown winner Justify.

The race lacked the retired three-year-old star with with Accelerate starting favourite.

He was in charge from the top of the straight and claimed his fifth consecutive Grade One victory to give Sadler his first Breeders' Cup win since his initial starter 30 years ago.

As for the California-based Accelerate being named this year's top thoroughbred, Sadler said he would leave that up to media who vote on the Eclipse Awards.

"To me, he's the Horse of the Year, no doubt," Sadler said. "He's won all those great races. To win the Santa Anita Handicap (in March) was for me probably one or two on my bucket list.

"The Classic is a newer race but a great race, and he won that so smashingly. He's just a great horse and had a great year."