Spurs coach Gregg Popovich said he thought the injury wasn't serious and that Duncan would be fine.
"I think he'll be OK, but what do I know?" Popovich told reporters after the game.
That is good news for a team that is finally healthy after spending much of the season battling a succession of nagging injuries to half its roster.
"They told us right away (Duncan's injury) was not big, so maybe half a second (of anxiety)," Spurs guard Tony Parker said.
Duncan left the game with about a minute remaining, clutching his elbow after teammate Tiago Splitter fell into him under the basket.
Duncan made the game's first basket on a follow of his own blocked shot 19 seconds in after failing to make a field goal for the first time in his career in San Antonio's previous game.
Duncan finished the Spurs' sixth straight victory with 12 points and 13 rebounds in 36 minutes.
Information from The Associated Press was used in this report.