Nets coach Avery Johnson said Saturday that Murphy had a "bad disk" and would be sidelined indefinitely. He does not think Murphy will require surgery.
Murphy will not accompany the Nets on their upcoming trip to Russia and China. He will be reevaluated when the team returns.
Johnson hopes Murphy might be able to practice in the week leading up to the opener against Detroit on Oct. 27.
Murphy was acquired this summer as part of a four-team deal. The New Jersey native has averaged 12.1 points and 8.6 rebounds in his previous nine seasons.
"We're concerned about his back," Johnson said. "He's just going to be out for a little while."
Johnson noted that Favors might be the team's starting power forward on opening night.
"It gives us a chance to prepare because we probably won't have [Murphy] to start the season," Johnson said.
Johnson said Murphy was working hard to get in shape for the season when his back started bothering him.
"Right now we're just going to plan on him not being there for the start of the season and if we get a surprise and his back responds well to this treatment and he can get back for a practice before the season starts then that will be a home run," Johnson said.