Sandoval sustained the injury on Tuesday, when he made perhaps his best defensive play of Spring Training.
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"He dove to his backhand side over against the Marlins the other day," said Red Sox manager John Farrell. "He was in here getting treatment most of the day yesterday and again today."
Farrell said that at this point, Sandoval is not in jeopardy of opening the season on the disabled list.
"The biggest thing is, we've got to get him back on the field first," said Farrell. "See if there are any restrictions physically. We've got to get him right and that's the next step in this, before anything solidifies before the opener."
Right-handed pitcher Koji Uehara, who hasn't pitched since Saturday, is also dealing with a nagging injury, with what Farrell termed "general soreness."
"He's going to be more aggressive on flat ground early today, throw a bullpen hopefully tomorrow, and then we look to get him in a game following that," Ferrell said.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.