The Astros placed Pressly on the 15-day injured list due to a lower-back strain, Matt Kawahara of the Houston Chronicle reports.
It's unclear when exactly Pressly sustained the strain, but he's given up one earned run in each of his last four outings. In his 10 outings since the All-Star break, he's recorded six holds and two blown saves with a 4.50 ERA and 1.80 WHIP over 10 innings. Seth Martinez was recalled from Triple-A Sugar Land in a corresponding move.