Decker signed a minor league contract with Boston and has been assigned to Double-A Portland, the Boston Globe reports.
Decker, who played eight games for San Diego last season, opened the 2016 season in the Padres' organization before being dealt to Colorado in April. The Rockies then released him in mid-May after he posted a .208/.246/.377 slash line while striking out 21 times in 52 at-bats. He's put up good power numbers during his career at the Triple-A level, but also strikes out a ton. For the Red Sox, he'll serve as organizational depth for a club that finds itself thin at the upper levels following Sam Travis' season-ending knee injury.