The Athletics selected Stefanic's contract from Triple-A Las Vegas on Tuesday.
The 30-year-old will get a look in the big leagues with the A's after signing as a non-roster invitee in December and failing to make the Opening Day roster. Stefanic's .250/.351/.355 slash line in 149 plate appearances at Triple-A this year is underwhelming, though he does have a 17:16 BB:K. He'll provide the club with some infield depth as Jacob Wilson (shoulder) heads to the injured list.