Tigers manager A.J. Hinch said Tuesday that Montero is on track to start Saturday's game versus the Dodgers, Evan Woodbery of MLive.com reports.
Pecko is slated to start Tuesday's game against the Yankees in New York.
Thaiss signed a minor-league contract with the Astros on July 24.
Rainey tossed two scoreless innings of relief in Monday's 4-1 loss to the Rays. He walked two and struck out two.
Valdez (8-9) took the loss against the Rays on Monday, allowing four runs (three earned) on eight hits and two walks in six innings. He failed to record a strikeout.
The Astros signed Velazquez to a major-league contract Monday, Matt Kawahara of the Houston Chronicle reports.
Delgado was optioned to Triple-A Sugar Land on Monday, Chandler Rome of The Athletic reports.
Lee will start at second base and bat second in Monday's game against the Rays.
The Tigers optioned Madden to Triple-A Toledo on Monday, Cody Stavenhagen of The Athletic reports.
The Tigers designated Vanasco for assignment Monday, Cody Stavenhagen of The Athletic reports.
