Putz, who was signed to a two-year contract as a free agent during the Winter Meetings, will be re-evaluated on Saturday.
"I just threw a couple of pitches in the bullpen and my back was stiff," Putz said. "It's just tight. It didn't feel right."
2010 Spring Training - null
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When he felt the stiffness, Putz called down to the dugout and told D-backs manager Kirk Gibson he was unable to pitch.
"You're always concerned," Gibson said. "We don't know anything about it. It may go away, it may just be a spasm. He's never had anything like that before. You certainly don't want your closer to go down."
Putz said he has never had back issues before and he was hopeful that it was nothing serious. He experienced some relief after the team's medical staff worked on him for a while in the trainer's room during the game.
"I have no idea what to expect," Putz said. "All I did was feel stiff. Instead of trying to pitch through it and go out there when you're not 100 percent, it's better just to give a call down and see what happens."
Following a schedule similar to the one he used while closing for the Mariners, Putz did not make his Cactus League debut until March 7. He then threw in a simulated game before appearing in his only other Cactus League contest on March 16, when he allowed four runs on two hits while walking three in just one-third of an inning.
As long as his back does not keep him out of action for a long period of time, Putz said it would not jeopardize his availability for Opening Day.
"There's plenty of time left," he said. "We've got two weeks left, I think -- there's plenty of time."