LOUISVILLE, Ky. — Sunland Derby winner Endorsement is out of the Kentucky Derby with an ankle injury and Interactif won't be entered in the Run for the Roses.

The changes allow Backtalk and Make Music for Me to become part of a full 20-horse field when the post position draw takes place later Wednesday.

Trainer Shannon Ritter said she noticed the ankle injury after Endorsement walked off the track at Churchill Downs following a half-mile workout Wednesday morning.

"We didn't even notice it right away," said Ritter, who was attempting to become the first female trainer to win the Derby.

The 3-year-old colt qualified with a win in the Sunland Derby on March 28. The race received graded stakes status this year after producing last year's Derby winner, Mine That Bird.

"It's disappointing for the whole WinStar family," said WinStar Farm racing manager Elliott Walden. "Hopefully he'll be back."

Trainer Todd Pletcher said Interactif is better suited for turf races and will bypass the Derby, which is contested over a dirt surface.

"He's better on the grass," Pletcher said. "Even though he trained well here, we felt that at 1 1/4-mile on the dirt, that's probably not his specialty."

The defection drops Pletcher to four starters in the Derby. He'll head to the paddock with Discreetly Mine, Mission Impazible, Super Saver and filly Devil May Care as he attempts to break his 0-for-24 mark in the signature race of the first Saturday in May.

Earlier this week, Pletcher lost expected favorite Eskendereya with an ankle injury, and Rule was declared out of the race following a subpar workout.

With preference given to the top 20 graded stakes earners, the changes allow for Backtalk and Make Music for Me to be eligible for the field. Jockey Robby Albarado, who was scheduled to ride Endorsement, will now ride Dean's Kitten in the Derby.