The 34-year-old Headley was reacquired from the New York Yankees along with right-hander Bryan Mitchell in the offseason. The Padres liked Mitchell so much that they were willing to take on Headley's $13 million salary.
But Headley was hitting just .115 (6-for-52) with no home runs and four RBIs at the time of Saturday's move. He had made only six starts at third base and three at first base.
Mitchell was demoted to the bullpen after going 0-3 in seven starts.