The Giants reinstated Mahle (hamstring) from the 15-day injured list ahead of his start Wednesday against the Athletics in San Francisco.
Before being shelved May 29 due to a left hamstring strain, the 31-year-old posted a 6.04 ERA, 1.54 WHIP and 57:24 K:BB in 56.2 innings. Tristan Beck was optioned to Triple-A Sacramento to make room on the active roster for Mahle, who could be operating with a workload restriction in his return to the rotation after covering three innings and tossing 63 pitches in his lone rehab start with Sacramento last week.