The 34-year-old featured for the full 90 minutes in the 3-1 win over Armenia on Friday, but has since picked up a muscle injury that kept him out of Sunday's training session.
"It is an injury that normally takes two or three days to shake off.
I'll play against Denmark if I'm feeling well, and miss the game otherwise,"
Buffon was quoted as saying by Corriere dello Sport. "We will just have to wait and see whether the treatment works."
Buffon's place between the sticks is likely to be taken by Napoli shot stopper Morgan De Sanctis, who has made only five international appearances so far, if he doesn't recover in time.
Italy are currently top of the table in Group B with seven points from three games.