This will be Gallardo's sixth straight opening day assignment. The previous five were with the Milwaukee Brewers. The Rangers acquired Gallardo, who went to high school in Fort Worth, in a four-player trade in January.
Gallardo, who is eligible for free agency after the season, becomes the seventh different Rangers' opening day starter in the past seven years.
Gallardo has an 11.32 ERA in three spring training games.
Yu Darvish was projected to start the Texas opener, but is out for the season after reconstructive elbow surgery on March 17.
Banister also announced left-hander Ross Detwiler has secured a spot in the rotation. Detwiler was used as a reliever last season by the Washington Nationals, but has 69 starts in his career. Detwiler is 0-1 with a 4.15 ERA in three spring appearances.