Nash, a two-time NBA MVP and six-time All-Star, left Monday night's game against Oklahoma City when his back started acting up in the first quarter. He had two assists and no points when he left the game, which the Suns won 110-102.
Nash, who has a history of back problems, said there was no particular event that caused the pain Monday night.
"Once in a blue moon I'll get back spasms," he said before the Suns' 101-89 win Tuesday.
Nash did not play the final 5 minutes of a Nov. 20 loss to the Los Angeles Lakers because of back issues. He has missed three games this season, but none were for back problems. One was due to flu-like symptoms, and another was because of a bruised right thigh. He also served a one-game suspension for his part in a shoving match between the Suns and Houston Rockets in November.
In his 13th year out of Santa Clara, Nash is tied for fifth in the league in assists with 8.3 per game and is third in free-throw shooting at 93.8 percent -- including a string of 27 straight. He ranks fourth on the Suns in scoring at 14.8 points a game.
The Suns have two days off before facing the Los Angeles Clippers on Friday.
Information from The Associated Press contributed to this report.