The Twins recalled Klein from Triple-A St. Paul on Saturday.
Klein has conceded two earned runs in just 2.1 innings with the Twins this season, but since being optioned to Triple-A on May 7, he's posted a 3.65 ERA and 0.89 WHIP with a 16:5 K:BB across 12.1 innings. Now back with the big club, he'll presumably work in a multi-inning role out of the bullpen, replacing Simeon Woods Richardson, who was DFA'd in a corresponding move.