Nowitzki, who left the 95-86 loss to the Grizzlies 51 seconds into the second quarter, said he hurt his back after taking a jump shot during pregame warmups. He tried to play, but was clearly hobbled. He left with one point and four rebounds in less than 10 minutes of action.
After retreating to the locker room to stretch and apply a heating pad in an attempt to loosen his back, Nowitzki said he finally decided to shut it down.
"I took a jump shot in warmups with 20 (minutes) on the clock and just the back locked up a little bit, went stiff," Nowitzki said. "I came back, tried to loosen it up, tried to play in the game, but it wasn't really loose enough to really do something.
"If I'm out there 50 percent, I'm not really helping much anyway, so (I) decided to take the night off, hopefully get some good treatment and have a big game on Friday. We definitely need to stop the bleeding. ... Hopefully, I'll be 100 percent."
The Mavs, already shorthanded with point guard Delonte West sidelined with a fractured finger and Lamar Odom away from the team for personal reasons, are two games into a stretch of nine games in 12 days.
They've lost three in a row and four of five. Dallas will have the Thursday off in New Orleans following the back-to-back before another back-to-back, starting with the Hornets on Friday and then the Utah Jazz at home on Saturday.
"Twenty-four hours, 48, basically until the next game is a long time for a body and I'll be able to get some treatment and recover, but I'm fully planning on it," Nowitzki said of playing Friday.
Nowitzki, being guarded by 7-foot-1 Grizzlies center Marc Gasol, started the second quarter but slowly walked off the floor less than a minute later and headed straight to the locker room with head athletic trainer Casey Smith.
Nowitzki, who does not have a history of back injuries, missed four games in January to strengthen his right knee. Since his return, the reigning NBA Finals MVP raised his scoring more than three points to 19.7 a game.
The Mavs are unsure of Odom's status for Friday, making Nowitzki's return all the more critical to turn their losing skid around.
"Hopefully it's minor," Mavs coach Rick Carlisle said. "Indications are that it's not serious, but we've got to see where we are (Thursday) and then Friday."
Jeff Caplan covers the Mavericks for ESPNDallas.com.