Three key players of the Korean World Cup squad -- Son Heung-min, Koo Ja-cheol and Ki Sung-yueng -- received controversial yellow cards during their first Group H match against Russia on Tuesday.
Media complained about Argentinian referee Nestor Pitana's overuse of yellow cards against the Korean players.
Pitana flashed his first yellow card as the Koreans tried to repel Russia's counterattack in 13 minutes into the game after Son allegedly tripped up Alexander Samedov from behind. But BBC commentator John Motson said that Son did nothing and probably did not deserve the yellow card.
In the 30th minute, Ki was given a yellow card while clattering into Samedov. The Daily Mail commented it the penalty was harsh.
Koo was shown his yellow card in the 90th minute while trying to deter a Russian attack.
But only one Russian player, Oleg Shatov, received a warning for an aggressive tackle against Koo in the 49th minute.
Pitana is one of the referees who are most liberal with yellow cards. He debuted as an international referee in March 2010, and Wednesday's game was his first World Cup match.
He has had a track record of issuing a total of 191 yellow cards, or 5.03 per match, in 38 international matches he refereed before the World Cup in Brazil.