Bochy said that Sandoval, who went 2-for-4 with a two-run single Thursday, wasn't certain how the injury developed. A particular plate appearance in which Sandoval slipped in the batter's box could have been the source, the manager noted.
Bochy said that the organization declined to place Sandoval on the 15-day disabled list, relying on the opinions of team doctors who believe that last year's World Series Most Valuable Player will be able to rejoin the lineup in much less than two weeks.
Bochy said that Sandoval wouldn't be able to pinch-hit Friday, but left that possibility open for the near future. Sandoval's batting .288 with a club-high 37 RBIs and eight homers, ranking second among the Giants.
Bochy chose Joaquin Arias over rookie Nick Noonan as Sandoval's replacement at third base on Friday. The manager hoped that Arias could recapture the impact he had last August, when he hit .417 in the month while Sandoval nursed a strained right hamstring.
"He needs the playing time," Bochy said of Arias, who had started only seven games, including two at third base, before Friday. "Last year he sparked us with his defense and his bat."
Right fielder Hunter Pence, who primarily has hit fifth, replaced Sandoval in the batting order's third spot.
Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.