Mushinski's contract was selected by the Astros on Saturday, Chandler Rome of the Houston Chronicle reports.
Mushinski made four appearances at Triple-A Sugar Land to begin the regular season, and he allowed an unearned run on a hit and no walks while striking out five in 4.2 innings. He'll now be available out of the Astros' bullpen to make his major-league debut, but he should pitch mainly in low-leverage situations.