Since being outrighted on June 27, Valverde has pitched in four games for the Mud Hens, compiling two saves but giving up two earned runs and five hits in four innings.
In his most recent outing, he allowed two earned runs on three hits against Triple-A Columbus.
"[Our goal] wouldn't be to keep him there for an extended time," president/general manager Dave Dombrowski said when the team designated Valverde for assignment. "It would be more of a matter of trying to get him fixed, and see if we can get him back to throwing the ball well and trying to get him back here."
Bobby Nightengale is an associate reporter for MLB.com.
This story was not subject to the approval of Major League Baseball or its clubs.