CHICAGO -- The routine act of taking off a pair of pants early Monday morning caused closer Brandon Morrow to suffer back spasms that prevented him from pitching the ninth inning of the Cubs' 4-3 loss to the Dodgers in the first game of Tuesday's split doubleheader.

"I was taking my pants off after getting home at 3 a.m." Morrow said as the Cubs returned late from St. Louis. "Got my right leg off. My left one, I felt spasms in my back."

Morrow, who has converted 16 of 17 save chances, believes the ailment isn't serious, adding his range of motion has improved. But his treatment consists of "kitchen sink."

"Everything they've got," said Morrow, adding that there are attempts to loosen the muscles in the front to relax the muscles in his back.

"I've gotten better. It's less grabby, like when I'm trying to touch my toes. But it was pretty evident I wasn't going to be able to pitch. It's a tough time getting socks on."

Morrow described his status as day-to-day.

The injury came a tough time for the Cubs, as Kyle Farmer hit a two-run double with two out in the top of the ninth off left-hander Justin Willson to wipe out the Cubs' 3-2 lead.

"(Wilson) has been throwing the ball really well as of late," Morrow said. "I thought he made some pitches that inning that could have gone either way. That's baseball."

Morrow said he wasn't in the bullpen in the ninth. His loss forced manager Joe Maddon to use Pedro Strop for the seventh and eighth innings.

"Otherwise, (Morrow) would have been pitching in the ninth," Maddon said.

Morrow has pitched only once since June 7.