If they have the same instructions as the Ark Derby, which were don't go with AP, they'll stay behind him. Here's some quotes from Lukas:
On paper, Mr. Z looked like one of only a couple of horses with enough early speed to challenge American Pharoah. But Lukas said he told Baffert he would not send Mr. Z after American Pharoah.

"I told Bob that I would not pressure him," he said. "For two reasons. No. 1, it makes no sense from Mr. Zayat's point. No. 2, it would have been suicidal to do that."

But once turning for home, all bets were off. "That's right," Lukas said with a laugh. "When we loomed up on the outside, I said, 'C'mon with him!'"

http://www.courier-journal.com/story/sports/horses/triple/derby/2015/04/14/kentucky-derby-wayne-lukas-says-american-pharoah-type-win-triple-crown/25760443/