Masterson agreed to terms with the Red Sox on Thursday, ESPN reports. After opening the season as the Indians' ace, Masterson experienced knee issues that landed him on the disabled list. After a deadline deal that sent him to St. Louis, the Cardinals made the call to move him to the bullpen, where he posted a disappointing 3-3 record and 7.04 ERA. It's unclear how the Sox intend to use Masterson, who began his major league career in Boston, but he'll likely be given an opportunity to prove he can return to a starting role.