Richards was optioned to the Rays' alternate site Monday to make room on the active roster for Ryan Yarbrough (groin), Juan Toribio of MLB.com reports.
Yarbrough will be activated from the 10-day injured list ahead of Tuesday's game in Washington, replacing Richards in the rotation. Though Richards will lose out on his roster and rotation spot, he could rejoin the Rays in a starting role as soon as Sept. 17, when he would likely pitch one half of a doubleheader with the Orioles.