Wolverhampton Wanderers manager Nuno Espirito Santo said he will not apologise for saying referee Lee Mason was not good enough for the Premier League after his team's 2-1 defeat at Burnley.
Nuno, who could face sanctions from the league's disciplinary body, made the comments following Monday's defeat at Turf Moor despite Mason giving Wolves a late penalty.
"I think I should apologise for the timing of my comments, probably they were not at the best moment... But I will not apologise for my words and my thoughts," Nuno told a news conference on Wednesday.
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"We expect high levels of performance, high standards... And what we expect from the referees, is for them to be confident to maintain their authority on the pitch. To control and handle the players and handle the game.
"The Premier League has the best system in referees and when we go to a match we expect a referee not to be a protagonist of the situation. We want the referee to let the game flow and especially to control the players."
The Football Association (FA) will decide whether to act upon the incident after receiving observations from the Portuguese manager, who will submit his response on December 29 when Wolves travels to Manchester United.
Under the FA Rule E3(1), a manager can be charged for post-match comments if those "imply bias, attack the officials' integrity or which are personally offensive in nature".