Marshall threw twice on rehab assignments this week and fared well before re-joining the team on Thursday in Washington.
Marshall last pitched on Wednesday for Triple-A Louisville, throwing 18 pitches in one inning. He said Thursday that he threw all of his pitches and felt fine.
He had pitched in just one game this season -- against the Nationals -- before going on the DL. Left-hander Parra went on the DL with a pectoral muscle strain (left), retroactive to Wednesday.
Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.