ESPN is reporting that some Niners fans started cheering and doing the wave after Arizona defensive end Calais Campbell was hurt during the game Sunday.
Several Niners players stepped in and gestured to the crowd to stop.
Campbell has since been released from a Bay Area hospital and returned home to Arizona.
Campbell was hospitalized for possible neck and spine injuries after he was carted off the field during Arizona's 32-20 loss at San Francisco on Sunday. The Cardinals say test results were favorable and Campbell was released from the hospital late Sunday night.
Campbell tweeted "a big thank you for all the support and kind words." He said he was feeling good and eager to return.
(Associated Press contributed to this story.)