Zenyatta was made the early 8-5 favorite in a field of 12 for the $5 million Breeders' Cup Classic, where she'll try to end her career with a 20-0 record.
Zenyatta will break from the No. 8 post in Saturday's 1 1/4-mile race against the boys at Churchill Downs.
At 6, Zenyatta is the oldest horse in the Classic, which she came from behind to win last year on Santa Anita's synthetic surface.
This time, she'll be running on dirt against an accomplished field that includes Preakness and Haskell winner Lookin At Lucky, Whitney winner Blame, and Quality Road.
Blame was installed as the 9-2 second choice Tuesday, while Quality Road was third choice at 5-1.
