Nets coach Avery Johnson said yesterday that Murphy has 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 the Pistons Oct. 27.

Murphy was acquired in the 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.’’

Derrick Favors, the No. 3 overall pick in the NBA draft, started for the Nets in their preseason game against the 76ers yesterday.

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.

The Nuggets said an MRI confirmed that Harrington partially tore the plantar fascia in his left foot during the first quarter of Denver’s 109-99 win over Portland Friday night.

Harrington is expected to start in place of Kenyon Martin, who will likely miss the first couple months of the season while recovering from knee surgery.

Harrington, who dealt with plantar faciitis in his left foot over the summer, was dribbling at midcourt in front of the scorer’s table when he came up limping just 79 seconds into his Nuggets debut.