In the third inning, Wood planted both feet awkwardly after he came off the mound to field Miami Marlins third baseman Jean Segura's bunt near the third-base line. He threw out Segura by a step but limped around the mound, prompting immediate attention from an athletic trainer and Giants manager Gabe Kapler.
"When I went to field the bunt, my cleat just stuck so hard," Wood said. "It's frustrating. As far as hamstrings, it's not that bad. We'll see how I wake up tomorrow and go from there."
Wood, 32, has not completed five innings in any of his three starts this season. He is 0-0 with a 1.80 ERA.
In a corresponding move, the Giants called up right-hander Tristan Beck from Triple-A Sacramento. Beck, 26, has yet to pitch in the majors, spending the past five seasons in the minors. He is 1-1 with a 3.38 ERA in three starts at Sacramento this season.
San Francisco optioned Stevenson to Triple-A Sacramento and designated left-hander Sam Long for assignment. The Athletics had designated Stevenson, 26, for assignment Friday.
Stevenson made his MLB debut last season and batted .167 (10-for-60) with one RBI in 23 games for Oakland.
Information from The Associated Press was used in this report.