With 7:17 left in the first quarter, Nash and Mavericks center Tyson Chandler collided while going for a loose ball in the Phoenix backcourt.
Nash's neck appeared to drive into Chandler's hip, and Nash was down for several minutes before limping to the bench.
"Just a weird night from that standpoint," Mavs forward Dirk Nowitzki said after the game. "We were all on the court; he's laying there screaming, 'I can't feel my hands.' So that was one of the weirdest things I've obviously ever seen, so very, very unfortunate. Hopefully he'll be OK. He's a warrior, and he'll recover quick."
Nash was replaced by Goran Dragic, and a few minutes later the Suns announced Nash was out for the rest of the game.
Afterward, Nash said he was intially scared.
"I just bumped my head at a weird angle and had a spinal-cord situation, lost feeling in my arms and legs," he said. "There were 10 seconds there that were really scary, but it came back and they just didn't feel like it was worth risking it tonight. We'll see how it goes tomorrow, but I'm optimistic about the amount that it improved already that hopefully I will be able to play Sunday or Monday."
Nash's absence obviously had a tremendous effect on the rest of the game. Dallas led by 12 at halftime and by as many as 24 in the third quarter. When Nash left, he had four points and an assist in less than five minutes. Jason Richardson was the only Suns starter to score in double-figures (12 points), and the NBA's top-scoring team at 109 points per game finished 18 points below its average.
"The game certainly changes without Nash; there's no question," Mavs coach Rick Carlisle said. "He's one of the best players ever. He's 2-for-3 when he went out four minutes into the game. He was very aggressive, and he was going to have a major impact on the game one way or the other. I hope he's OK."
Information from ESPNDallas.com's Jeff Caplan and The Associated Press was used in this report.