Volquez had struck out nine before leaving his most recent start May 2 in the fifth inning due to the blister. He said the ailment made it difficult to grip the baseball and have command of his pitches.
He is 0-4 this season with a 4.71 ERA.
In a corresponding move, right-hander Brian Ellington was optioned to Triple-A New Orleans. Ellington had made two relief appearances in the past week, allowing five hits but zero earned runs in 3 2/3 innings.