Choo is expected to be sidelined 4-6 weeks with a strained right calf muscle, while Chirinos is expected to be out 10-12 weeks with a fractured right forearm. Chirinos was placed on the 60-day disabled list.
Mazara, a left-handed hitter, is coming up to be the everyday right fielder while Choo is sidelined. He was in the lineup batting second on Sunday.
"We are going to give him all the opportunity and see how it plays out," Rangers manager Jeff Banister said. "I like the fact he controls the strike zone, can be patient and can jump on a fastball early, if needed. The offspeed [pitches] in Spring Training didn't bother him. With [Delino DeShields] hitting in front of him, he can be patient if we want to run, he can hit down in the count, and I like the on-base potential."
The Rangers have Ryan Rua, who can play right field. But right now, Mazara has the job and Rua remains the fourth outfielder. Justin Ruggiano, who was outrighted to Round Rock, has accepted the assignment.
"Obviously we like Ryan and we like what he does," Banister said. "We like the versatility. Ryan is going to get the opportunity to play."
Mazara, signed as an amateur free agent for a $4.95 million bonus out of the Dominican Republic in 2011, is the No. 3 prospect in the Rangers' organization, according to MLBPipeline.com, and No. 17 in the overall Top 100. He was Texas' Minor League Player of the Year in 2015 after hitting a combined .296 with 26 doubles, 14 home runs and 69 RBIs in 131 games between Double-A Frisco and Round Rock.
Mazara also had a good Spring Training with the Rangers, going 12-for-32 (.375) with one home run. He was 6-for-12 with one home run in three games for Round Rock.
"This is what I dreamed of as a little kid, but it's sad news because Choo got hurt," Mazara said. "You don't want anyone to get hurt."
Mazara is 20 years old, with a birthday coming up on April 26.
"I don't want to put too much pressure on myself, just go out and have fun," Mazara said. "I know all the guys around me; that will make me more comfortable."
Mazara is likely to be here only while Choo is sidelined. But that doesn't stop him from hoping it will be a permanent promotion.
"When you come to the big leagues, you want to stay as long as you can," Mazara said. "Choo is hurt, so I don't know what they will do. I hope he gets well fast. I don't know how long he will be out, but I want to do well why I am here."
Fantasy spin | Fred Zinkie (@FredZinkieMLB)
The loss of Choo is a significant one for mixed-league teams, but Mazara could be a viable replacement during the coming weeks after posting an impressive .296/.366/.443 slash line across two Minor League levels in 2015. The 20-year-old is unlikely to steal many bases, but he can post a respectable batting mark and rip a few round-trippers during Choo's absence. And if he is consistently slotted into a premium lineup spot, the youngster could also score runs at a great rate. Mazara should be added in virtually all five-outfielder leagues, and Choo owners should use bench or disabled-list space to retain the 33-year-old -- who produced a .343/.455/.560 slash line in the second half of '15 -- during his absence.