Perez, a 22-year-old left-hander, has made seven career starts, including one this season on May 27 in the first game of a doubleheader in Arizona. He allowed three earned runs in 5 1/3 innings in a 5-3 loss to the Arizona Diamondbacks and was optioned back to Triple-A Round Rock.
Perez has been on a roll since then, going 4-0 with a 1.13 ERA in four starts for the Express.
"I have a lot of confidence on the mound," Perez said. "I'm not going to try to do too much."
With Perez starting Saturday, rookie Nick Tepesch will be bumped back a day to start the ESPN Sunday Night Baseball Game at St. Louis.
Rangers ace Yu Darvish also is having his start pushed back and will pitch the opener Tuesday at Yankee Stadium against New York.
"There's not fatigue with Darvish," Rangers manager Ron Washington said. "We're going to push our guys back a day or two when he get the chance."