Ragans' contract was selected from Triple-A Round Rock ahead of Thursday's start against the White Sox.
Ragans was a first-round pick in 2016 and will make his major-league debut during Thursday's series opener at Globe Life Field. The left-hander was promoted to Round Rock in mid-June and posted a 3.32 ERA and 1.07 WHIP in 43.1 innings over eight Triple-A starts. If Ragans performs well Thursday, it wouldn't be surprising to see him remain in the Rangers' rotation.