Kentucky Derby winner American Pharoah is the odds-on favourite in the Preakness Stakes despite drawing barrier one, a gate which has not produced a winner in more than two decades.

A field of eight three-year-olds will go to the post on Saturday (Sunday AEST), the smallest since 2000 when Red Bullet upset Derby winner Fusaichi Pegasus.

Trainer Bob Baffert is looking for his sixth Preakness win with American Pharoah and Dortmund, who drew No.2.

Third in the Derby, Dortmund was the 7-2 second choice behind American Pharoah at 4-5 with Derby runner-up Firing Line (4-1) to start from the outside.

Baffert has never liked barrier one and and history backs him up.

The last horse to win the Preakness from the inside post was Tabasco Cat in 1994 and the last to win from two was Snow Chief in 1986.

"I can't believe I drew the 1-2," Baffert said.

"It's the luck of the draw. I don't love it."

If American Pharoah wins, it would set Baffert up for an unprecedented fourth Triple Crown try. The last Triple Crown winner was Affirmed in 1978.

Victor Espinoza has the mount on American Pharoah, with Martin Garcia aboard Dortmund and veteran Gary Stevens to ride Firing Line.

The field, from the rail out is: American Pharoah (Espinoza, 4-5); Dortmund (Garcia, 7-2); Mr. Z (Corey Nakatani, 20-1); Danzig Moon (Julien Leparoux, 15-1); Tale of Verve (Joel Rosario, 30-1); Bodhisattva (Trevor McCarthy, 20-1); Divining Rod (Javier Castellano, (12-1); and Firing Line (Stevens, 4-1).