The entry box for the derby closed Wednesday morning and a drawing will be held to later Wednesday as only 20 horses will get to run.
Leading the way is Bodemeister, the dominant winner of the Arkansas Derby and one of two horses in the field trained by Bob Baffert. He also has Liaison.
Todd Pletcher also will saddle two -- Wood Memorial winner Gemologist and Risen Star winner El Padrino.
Michael Matz, who won the 2006 Derby with Barbaro, trains Fountain of Youth winner Union Rags.
Optimizer will be the record 45th Derby starter for trainer D. Wayne Lukas, a four-time winner of the race. The colt got into the field when Mark Valeski was withdrawn from consideration Tuesday.
The 21st horse on the earnings list is My Adonis, an also eligible who would need a defection to get into the 1 1/4-mile race.
Other entries for the 138th Derby are Withers winner Alpha, San Felipe winner Creative Cause, UAE Derby winner Daddy Long Legs, Sunland Derby winner Daddy Nose Best, Illinois Derby winner Done Talking, Blue Grass winner Dullahan, Gotham winner Hansen, and Santa Anita Derby winner I'll Have Another.
The rest of the entries are Tampa Bay Derby winner Prospective, Rousing Sermon, Sabercat, Florida Derby winner Take Charge Indy, Bay Shore winner Trinniberg, and Spiral Stakes winner Went the Day Well.
The Associated Press contributed to this reports. All rights reserved.