"It's better than it was last night," Headley said Wednesday. "Last night and again this morning when I woke up, there were spasms. It's not great by any means."
Logan Forsythe made the start at third base in the series finale against the D-backs. Headley won't play at all in the game and will get an additional day of rest on Thursday as the team is off. The Padres will open a three-game series at Dodger Stadium on Friday.
"We'll see where we are when we get to L.A.," said Padres manager Bud Black.
Headley doesn't anticipate his back being a lingering issue beyond Thursday.
"It just needs a little time," he said. "But I don't anticipate it being more than a day or two."
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.