Blanks comes to the big leagues off a hot streak put together at Triple-A Round Rock. After starting the season 0-for-12, he had 17 hits in his last 40 at-bats with three home runs and 16 RBIs.
Moreland underwent surgery to have a bone chip removed from his left elbow on Wednesday and is expected to be sidelined for 2-3 weeks. Moreland's last four starts had been at first base while Fielder's last five have been at designated hitter.
Blanks, who has appeared in 260 games over the past six seasons with the Padres and Athletics, has had twice as much Major League time in the outfield than he has at first base. But the Rangers limited him to first base in Spring Training because of his long history of injuries.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.