"The back is still bothering him," Black said before Sunday's series finale against the Dodgers. "He was making progress and that has sort of reached a plateau. He didn't quite make the progress in the next 24 hours that he did the first 24."
Headley had been heating up at the plate, with a hit in 10 of his past 12 games. In 117 games with the Padres this season, he's hitting .240 with eight home runs, 28 doubles and 36 RBIs.
Last year, Headley was the National League Player of the Month in August and won the award again in September. This year, he was limited to 21 games in August and hit .261.
Alexi Amarista started at third base on Sunday.
Austin Laymance is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.