Guerra (elbow) was activated from the 60-day injured list Tuesday.
Guerra has been on the injured list all season while recovering from a sprained UCL in his right elbow, but he'll join San Diego's active roster for the closing stretch of the season. The 25-year-old figures to fill a low-leverage role out of the bullpen now that he's healthy. Jake Arrieta (groin) was designated for assignment in a corresponding move.