This will be Klein's third stint with the Rangers this season. He last pitched in a start May 25 against the Indians and is 1-0 with an 8.25 ERA in eight games. Klein is 1-0 with a 0.91 ERA this season in 12 appearances for Round Rock. He has made four starts in Triple-A and should be a suitable long-relief option.
Texas relievers allowed a season-high nine runs Sunday in a 13-7 loss to the Angels. Six pitchers appeared in the game.
Bass' 51 2/3 relief innings rank second in the American League, and he leads the Majors with six relief outings of at least 3 2/3 innings.