Perez, who will not play for Venezuela any more in the Classic this spring, originally was scheduled to be back at Royals camp Sunday night.
"The doctors didn't want him flying right away," Royals manager Ned Yost said. "There might be a little fluid on his knee. They wanted to give him a day for that to settle down."
Perez is expected to have a second MRI on Tuesday. The Royals' medical staff wants the second MRI as confirmation there are no lingering issues with Perez's knee.
"They're very cautious until they get their hands on him," Yost said.