The Mariners selected Fairchild's contract from Triple-A Tacoma on Saturday.
Fairchild will join the active roster as a replacement for Luke Raley, who landed on the injured list Saturday with an elbow injury. Fairchild has gone just 3-for-19 with an RBI, three runs and two steals in the majors this season, but he's slashed .262/.415/.643 across 53 plate appearances since joining Tacoma on July 10.