FIFA has launched an investigation after claims that Luis Suarez bit Giorgio Chiellini in Uruguay's 1-0 victory over Italy.
Suarez, who served a 10-match ban for biting Chelsea defender Branislav Ivanovic in 2013, appeared to bite Chiellini on the shoulder in the 79th minute of the match.
Television replays showed Suarez moving his head towards Chiellini who responded by swinging an arm, before chasing the referee to insist he had been bitten.
A FIFA spokesperson said: “We are awaiting the official match reports and will gather all the necessary elements in order to evaluate the matter.”
FIFA's disciplinary code sets a maximum ban of 24 matches or two years, but the longest ban in World Cup history was eight games for Italy's Mauro Tassotti for breaking Spain's Luis Enrique's nose in 1994 with an elbow.
The incident, over which the referee took no action, took place shortly before Diego Godin's late goal sent Uruguay through to the World Cup knockout stages at the expense of 10-man Italy in Natal.
Suarez could face suspension if FIFA disciplinary officials uphold Chiellini's protests, and the incident cast a shadow over a hard-fought win for the South Americans.
However, the player himself sought to downplay the incident, reportedly telling Uruguayan media that "these things happen in the box" and that people should not make such a big deal of it.
Suarez suggested Chiellini had bumped into him during the incident.
Speaking afterwards to Gazzetta, Chiellini said: "The disparity in judgement has been evident. Marchisio's sending-off was ridiculous but more so the fact that Suarez wasn't sent off.
"There's the will to protect champions but... The referee should have shown him a red card. There's a clear simulation after, a clear sign that he had done something that he wasn't supposed to.
"The gesture is clear. Referees document themselves on players and Suarez has a very clear history.
"The referee has given a clear address, he hasn't spoken throughout the game. These are episodes that condition. The only way they could have hurt us was from set pieces and so it was."