The Liverpool star appeared to bite the defender during a tussle in the Italy area, with the Juventus man attempting to show the referee the mark on his shoulder following the incident.
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"Are you sure you saw a bite?" Lugano said to reporters when questioned.
"Because I've watched the incident again and I saw nothing...
"I've seen the picture of Chiellini. That scar isn't from today's game. You have to be very stupid to believe that scar is from now.
"Italy had been wasting time the entire match, provoking us on the pitch like they always do.
"I never believed an Italian player could be such a coward off the pitch. During the game, yes, it is all part of football, but I think the manly thing to do would be to just accept defeat. To denounce your opponents just out of bitterness is bad.
"There was no bite and there was no scar."
Cristian Rodriguez, meanwhile, also downplayed the incident before hailing defender Diego Godin's influence following his matchwinning goal.
"We are all men. I think it was nothing, I didn’t see anything and I think there will not be consequences," he said.
"Godin's goal was no coincidence. He is a player who is very strong in the air and has scored important goals."
Uruguay will meet Colombia in the round of 16.