Shawaryn had his contract purchased from Triple-A Pawtucket on Thursday.
Shawaryn will take the roster spot of Hector Velazquez (back), who was sent to the injured list in a corresponding move. The right-hander has strictly work as a starter for the PawSox this season -- compiling a 3.72 ERA and 1.32 WHIP in 10 starts (55.2 innings) -- so he figures to fill the long-relief role left open by Velazquez.