Valdez is scheduled to start Tuesday's series opener against the Dodgers, Chandler Rome of the Houston Chronicle reports.
The 26-year-old and Brandon Bielak were competing for the final rotation spot during summer camp, but Valdez was able to secure the job. Valdez had a 5.86 ERA and 1.67 WHIP over 70.2 innings at the major-league level last season, and he may not have a long leash if he struggles again during the shortened season. Jose Urquidy (undisclosed) and Austin Pruitt (elbow) aren't available to start the season but figure to be options for the rotation eventually, and Bielak could also remain a factor.