A total of 166 horses, including 37 from Europe, were pre-entered yesterday for the $25.5 million, 14-race Breeders’ Cup world championships at Santa Anita Nov. 6-7. That’s down from last year’s record of 180 horses.

Zenyatta was pre-entered in both the Classic, along with Kentucky Derby winner Mine That Bird and Belmont and Travers winner Summer Bird, and the $2 million Ladies’ Classic.

But her connections are leaning toward the Classic Nov. 7, pending the outcome of the 5-year-old mare’s final 6-furlong workout Saturday at Hollywood Park.

“There’s definitely a preference for the Classic,’’ trainer John Shirreffs said. “The Classic is obviously a big challenge, but if she’s doing well and peaking towards that race, there’s no reason not to go in that race.’’

Final entries and the post-position draw will be Tuesday.

Zenyatta has won all four of her starts this year. If she wins either race, she will surpass the mark of Personal Ensign, who won all 13 of her career races.

“I’m always amazed at how well she performs,’’ Shirreffs said. “This is like a stopper on a baseball team. When you’re not doing so well, you bring out Zenyatta and she lifts the whole barn.’’

Zenyatta won the Ladies’ Classic last year on Santa Anita’s synthetic Pro-Ride surface.

“The advantage of going in the Ladies’ Classic is you have a great shot to win that race and it’s a very large purse,’’ Shirreffs said. “You have probably a better chance of winning there.’’

But if Zenyatta were to run against the boys for the first time - and win - she would make a strong case for Horse of the Year. Her Hall of Fame jockey Mike Smith has endorsed testing her against male competition in the Classic.

“She’s going to be very, very tough to beat,’’ said Alistair Donald of the International Racing Bureau. “If Zenyatta goes in the Classic, I fully expect her to be favored.’’

Horse racing’s richest two days is returning to the same track for the first time in consecutive years. The track’s surface, however, will prevent a showdown between Zenyatta and Preakness winner Rachel Alexandra, whose owner refused to run his sensational filly because he dislikes synthetic surfaces.

Breeders’ Cup president Greg Avioli was clear about which race he wants to see Zenyatta in.

“It’s going to be a bigger story for the sport if she chooses to run in the Classic,’’ he said.

The full field of 14 pre-entries for the 1 1/4-mile Classic include Irish standouts Rip Van Winkle and Mastercraftsman, who is more likely to run in the Dirt Mile; Arlington Million winner Gio Ponti; and Santa Anita Handicap winner Einstein.

Other Classic pre-entries include Pacific Classic winner Richard’s Kid, trained by Bob Baffert, and Quality Road, trained by Todd Pletcher. Quality Road, an early Kentucky Derby favorite, missed the race because of injury.