Manager Ned Yost said that Pina suffered a torn meniscus in his right knee during a batting practice mishap on Wednesday. He's expected to be out at least four weeks.
"The extent to what we're looking at time-wise will be determined when they get in there and see where it's at and how bad it's torn," Yost said.
Pina might return to KC on Sunday with Dr. Vincent Key, the head team physician, and undergo surgery at the University of Kansas Medical Center.
The injury means that Brayan Pena, with whom Pina was competing for a job, likely will open the season as the backup to regular catcher Salvador Perez. Pina's injury deals a blow to the Royals' catching depth.
Other catchers still in camp are Cody Clark, Max Ramirez and Julio Rodriguez. Minor League catchers Ben Theriot and Ryan Eigsti will be shuttled in as needed. Of those five catchers, only Ramirez has any big league experience.
Pina was injured on a routine play while catching during batting practice.
"There was nothing he could have done. It was a fastball and a pitch where he shifted a little bit on a foul ball. He moved and his spike caught," Yost said. "It was one of those freak things."