Paolo Di Canio: PFA investigates decision to fine Sunderland players
The disciplinary action taken by Paolo Di Canio against several Sunderland players is being investigated by the Professional Footballers' Association.
Players' union chief Gordon Taylor said the Black Cats manager could not be "a law unto himself".
Taylor said the PFA would determine if the punishments were "acceptable" or if there were grounds for an appeal.
"I wouldn't want to go any further at this moment, so as not to prejudice any particular situation," he said.
Taylor admitted there had been contact between the PFA and Sunderland players already, while discussions had also been held with the Premier League club.
"There has been some complaints, yes," said Taylor.
Di Canio took over from Martin O'Neill as manager of the Wearside club in March and has won two of his seven games in charge to help the club avoid relegation.
The 44-year-old Italian was scathing about the behaviour of some of his players following the 1-0 defeat at Tottenham on the final day of the season.
Black Cats defenders Phil Bardsley and Matthew Kilgallon were left out of the squad for the game at White Hart Lane, having been pictured in a casino in midweek.
"Nobody says we're against discipline at the PFA. but it's got to be proportionate," said Taylor. "We have a recommended code for clubs to adhere to.
"Players know when they've done wrong and when they've been a problem. For the most part, they will accept that.
"But it's not always good to have the manager coming out in public. These things are better dealt with person to person internally and it's better for the future."
Fifteen years ago, Di Canio was represented by Taylor after pushing over referee Paul Alcock in 1998 when he was a Sheffield Wednesday player.
"I can remember representing him many years ago when he had his problem with the referee at Sheffield Wednesday," said Taylor.
"I don't want to add fuel to the flames, merely to say Paolo was a player and member of the PFA.
"The PFA were there for Paolo when he was a player and we'll be there for him with his players. He is aware of the role of the PFA and knows we are there for the players.
"Paolo can't be a law unto himself. There are rule and regulations to abide by - and that goes for the disciplining of players as well."