The Royals and Mariners were rained out Saturday night and rescheduled for a traditional doubleheader Sunday, starting at 1:15 p.m. CT with about 30 minutes between games.
Perez left Friday’s game after six innings, and an MRI revealed that he has a strained intercostal muscle on the right side of his chest.
“It’s going to have to be a pretty miraculous recovery,” Royals manager Ned Yost said of what it would take for Perez to avoid the disabled list.
It they had played Saturday, Yost said Perez was “too sore” to play. The Royals had rookie catcher Cameron Gallagher in the clubhouse on standby, ready to activate him.
The Mariners recalled left-hander Marco Gonzalez from Triple-A Tacoma to take Hernandez’s rotation turn. Gonzalez will start the first game Sunday, and the Royals will counter with left-hander Danny Duffy.
Gonzales was acquired in a July 21 trade with the St. Louis Cardinals for outfielder Tyler O’Neill. He went 2-0 with a 4.50 ERA in two starts with Tacoma.
The Mariners will start right-hander Erasmo Ramirez in the second game. The Royals plan on bringing up rookie right-hander Jakob Junis as the 26th man and starting him in the second game.
Junis is 3-2 with a 5.50 ERA in nine games, six starts, with Kansas City. He is 3-5 with a 2.92 ERA in a dozen starts with Triple-A Omaha this season.
The rainout was the Mariners’ first since April 30, 2014. They had not been rained out in Kansas City since Aug. 19, 2004.