Boston also designated first baseman/outfielder Sam Travis for assignment to make space on the 40-man roster, chief baseball officer Chaim Bloom said Thursday.
The 28-year-old Plawecki is a five-year big league veteran with the New York Mets and Cleveland Indians. He's a career .218 hitter and batted .222 with three homers, 17 RBI and a .629 OPS in 59 games with Cleveland last season.
Travis, 26, was a second-round pick by Boston in 2014. He's struggled in brief major league stints since debuting in 2017, batting .230 with seven homers and a .659 OPS over 111 games.