Valdez will move to the bullpen as the Astros employ a four-man starting rotation for the final few weeks of the season, Brian McTaggart of MLB.com reports.
The 25-year-old allowed 10 runs on 13 hits with a 19:14 K:BB over 15.2 innings in three starts since rejoining the rotation in late August, but Houston will take advantage of scheduled off days and September's expanded roster to cover the instances when a fifth starter is necessary. Valdez has a 5.62 ERA, 1.61 WHIP and 64:40 K:BB through 65.2 innings this season.