Madrid - The Champions League battle of Madrid left Atletico striker Mario Mandzukic with a bloodied face and controversy over whether he was bitten by Real defender Dani Carvajal.
Carvajal strongly denied even trying to bite the Croatian striker. But he could still face action for landing a punch at Mandzukic that the referee did not see.
Madrid newspapers speculated that the 23 year-old Spanish international could be suspended for next week's return match in their Champions League quarter final.
The tie was left 0-0 after Tuesday's first leg at the Vicente Calderon stadium, but there was much spotlight on the Carvajal-Mandzukic clash.
Battling in the penalty area, Mandzukic's arm is raised to hold back his rival. As Carvajal moves round, his mouth comes close to Mandzukic's arm and then he lands a punch in the striker's stomach.
Serbian referee Milorad Mazic was unsighted and Carvajal was extremely lucky not to concede a penalty for the punch. But the images soon dominated social media and Carvajal, who could still face retroactive action by UEFA, was quick to react on his Twitter account.
"I saw after the game that I am accused of biting an opponent player, I want to clarify that I have not bitten anyone, nor attempted to," he said.
Film from the mixed zone after the game, broadcast by Spanish channel Neox, showed a small cut on Mandzukic's arm. But there was no way of telling whether it was a cut.
The 28-year-old Croatian had already been in the wars.
He was left with a bloody nose thanks to a stray elbow from Madrid defender Sergio Ramos.
Carvajal's absence for the second leg would be a blow for Real Madrid next Wednesday. They will already be without another key defender Marcelo who reached his yellow card limit in the game.
Football bites have been a major talking point since Uruguayan Luis Suarez was banned from all football activity for four months last year for sinking his teeth into Italian World Cup opponent Giorgio Chiellini.