Gallo will take the roster spot of Adrian Beltre, who heads to the 15-day disabled list with a sprained thumb and laceration.
Baseball America ranked Gallo as the Rangers' No. 1 prospect and the No. 6 prospect overall heading into the 2015 season.
The 21-year-old Gallo has been playing at Double A Frisco, where he has a .314 average with nine home runs, 31 RBIs and a .636 slugging percentage in 34 games. He has also struck out 49 times.
Gallo was selected to play in last year's All-Star Futures Game as a member of the U.S. team. In time split between Double A and Advanced Single A in 2014, Gallo hit 42 home runs with 88 RBIs and 179 strikeouts.
The Rangers (28–25) are currently in third in the AL West. They host the Chicago White Sox on Tuesday.
- Molly Geary