Sandoval is just two-and-a-half seasons into the five-year, $90-million contract he signed with Boston in 2015. He's earning $17 million this season, $18 million in 2018 and 2019, and another $17 million in 2020 - all of which the Red Sox are still on the hook for. He does have a $5-million buyout in his contract for 2020, however.
After seven years with the San Francisco Giants, the 30-year-old Sandoval has appeared in just 161 games over three seasons with the Red Sox, where he's recorded a .237/.286/.360 slash line and hit 27 home runs.
Sandoval was in the middle of a rehab assignment after being diagnosed with an ear infection in June.
A two-time All-Star and three-time World Series champion, he's hitting .285/.337/.449 with 120 home runs in his 10-year career.