Controversial trainer Bob Baffert seeks a fifth Breeders' Cup Classic crown while rival Brad Cox chases his first Classic victory with two oddsmakers' darlings in the 38th annual thoroughbred showdown that begins Friday.

The $6 million Classic caps two days of Breeders' Cup showcase racing at Del Mar, with five juvenile events Friday at the classic Southern California venue plus nine races on Saturday and more than $31 million at stake.

Baffert, 68, brings Kentucky Derby winner Medina Spirit to the Classic after the horse tested positive for a banned substance following his win at Churchill Downs.

"He likes this track and is training really well coming up to the race," said Baffert, who won his fourth Classic title last year with Authentic.

Medina Spirit tested positive for a banned substance at the Derby and after placing third at the Preakness was banned from the final Triple Crown event, the Belmont Stakes.

The Kentucky Horse Racing Commission is investigating the matter while Churchill Downs issued a two-year ban on Baffert, who filed suit in June demanding more tests before his horse could be stripped of the Derby win.

Baffert, the all-time money leader among Breeders' Cup trainers, was allowed to enter horses this week, but had to submit to tighter barn security and stricter out-of-competition testing for banned substances than his rivals.

Jockey John Velazquez, who rode Medina Spirit to his Derby win, was aboard the colt for wins at Del Mar and Santa Anita in Breeders tuneup races and rides again Saturday from the eighth stall in the nine-horse field for the 1 1/4-mile showdown.

Medina Spirit and Hot Rod Charlie, winner of the Pennsylvania Derby, are 4-1 choices for the Classic.

But the favorites belong to Cox, 41, who has never before had a starter in the Classic, although his horses have captured seven Cup titles, including a record-tying four 2020 triumphs.

This year, Cox boasts the Classic favorites in 2020 Breeders' Cup Dirt Mile winner Knicks Go, the 5-2 morning line favorite ridden by Joel Rosario, and 2020 Juvenile winner Essential Quality, the Luis Saez-mounted second choice at 3-1.

"I'm excited about being in this position with both horses," Cox said.

Controversial trainer Bob Baffert will enter Medina Spirit, who tested positive for banned substances after winning the Kentucky Derby, in Saturday's Breeders' Cup Classic at Del Mar
Controversial trainer Bob Baffert will enter Medina Spirit, who tested positive for banned substances after winning the Kentucky Derby, in Saturday's Breeders' Cup Classic at Del Mar GETTY IMAGES NORTH AMERICA / ANDY LYONS

Knicks Go will start from the fifth gate with 2021 Belmont Stakes winner Essential Quality just one gate inside.

"It's very rare for a horse to do what Knicks Go can do," Cox said. "You don't always see horses that are capable of running as quick as he can and clearing. And he really accelerates in the turns."

Essential Quality's only loss in his past nine starts came at the Kentucky Derby, when he finished fourth.

"It does set up well," Cox said. "That's the one great thing about Essential Quality. He's able to adjust to the pace and that's what makes him so dangerous each and every run."

The $4 million Breeders Cup Turf is a 1 1/2-mile showdown on the grass course that attracts top horses from around the world.

Ireland's Tarnawa beat the boys in last year's Turf and is back as a 9-5 favorite coming off a runner-up finish at the Prix de l'Arc de Triomphe. Jockey Colin Keane is back aboard and will leave from the 13th of 14 gates.

The $2 million Distaff matches the top fillies and mares over 1 1/8-miles with Letruska the 8-5 favorite. She has won five starts in a row and six of seven this year, her past three over the same distance as the Distaff.

Defending champion Audarya returns in the $2 million Filly & Mare Turf. The 5-1 French horse starts from the outside in a field of 12 over the 1 3/8-mile distance.

Favored War Like Goddess breaks from the number seven post at 7-2 odds seeking a fifth consecutive victory.

Friday's Juvenile, the feature in a set of races for 2-year-olds, will determine early favorites for next year's Triple Crown races.