Manager John Farrell said Tuesday that Masterson will work out of the bullpen after being a starter before going on the disabled list with right shoulder tendinitis. He is 2-2 with a 6.37 ERA in seven appearances.
The Red Sox claimed Kratz off waivers from Kansas City on Sunday after he was designated for assignment. In four games with the Royals this season, he was hitless in four at bats.
Wright is 3-2 with a 4.15 ERA in 11 games, four of them starts. Castillo is batting .230 with one homer and six RBIs in 14 games.