Gallen had his contract selected from Triple-A New Orleans ahead of his scheduled start against the Cardinals on Thursday, Jordan McPherson of the Miami Herald reports.
As expected, Gallen is set to make his big-league debut in place of the injured Pablo Lopez (shoulder). The 23-year-old right-hander was dominant through 14 starts with New Orleans prior to earning a promotion, compiling a 1.77 ERA, 0.71 WHIP and 112:17 K:BB in 91.1 innings. Gallen should have a good chance to stick in the rotation for more than one turn if he performs well Thursday. Jeff Brigham was optioned to Triple-A and Peter O'Brien was designated for assignment in a pair of corresponding roster moves.