The Rays optioned Muller to Triple-A Durham on Monday.
Muller received his first MLB call-up Friday and spent the weekend with the big club, but he didn't get the chance to make his debut during the Rays' series with the Yankees. He'll now head back to Durham with the Rays needing to free up a roster spot for closer Pete Fairbanks (forearm), who was reinstated from the 15-day injured list Monday.