The Astros reinstated Whitley (knee) from the injured list Saturday, Chandler Rome of The Athletic reports.
Whitley landed on the injured list at the start of the season due to a bone bruise in his left knee. He has since made four rehab appearances at Triple-A Sugar Land, allowing three runs while striking out five batters and walking four over 3.2 innings. He'll almost certainly work in low-leverage situations for the Astros; meanwhile, Nick Hernandez will head back to Triple-A.