Professional Footballers' Association chief Gordon Taylor fears for Luis Suarez's career following the Liverpool striker's latest 'biting' incident.
The Uruguayan could face a possible two-year or 24-match ban if found guilty of biting Italy's Giorgio Chiellini at the 2014 Fifa World Cup.
The 27-year-old has twice been punished for biting opponents and any suspension could be extended to domestic football.
"It is a big problem for Liverpool," said Taylor. "I fear for his career."
Fifa has opened disciplinary proceedings following Tuesday night's incident and has given Suarez and the Uruguayan Football Association until 21:00 BST on Wednesday to respond.
Suarez has been banned twice before for biting opponents, once as Ajax skipper and most recently with Liverpool.
After biting Chelsea's Branislav Ivanovic during a Premier League match in April 2013, he was given a 10-game ban.
The Uruguayan missed the start of last season as a result but returned to help Liverpool finish second in the table.
He also picked up two prestigious accolades, voted the PFA's Player of the Year and Football Writers' Player of the Year.
"He seemed to get back on track," Taylor told BBC Radio 5 live. "He had a great season."
Fifa has never extended a ban for a non drugs-related incident to domestic football, but there are calls for world football's governing body to hand out a significant punishment to Suarez.
Former England captain Alan Shearer and ex-Wales midfielder Robbie Savage believe the Uruguayan should get a lengthy suspension, while ex-England midfielder Paul Scholes said banning him for the rest of the World Cup was "not enough".
Taylor said the PFA would help Suarez in any way it could to "eradicate" any issues he may have, a sentiment echoed by former England manager Graham Taylor, who said Suarez now required psychological assistance.
"This is a person who definitely needs help," the ex-Aston Villa boss told BBC World Cup breakfast.
Former Liverpool midfielder Jan Molby expects his old club to be criticised whatever they do but thinks they should fight to retain Suarez.
"Some people will say they should wash their hands of him, but there's no chance of that," Molby told the Liverpool Echo. "He's their only genuinely world-class player. Whatever Liverpool do now, they will be criticised."
Reds legend Robbie Fowler would not be surprised if Suarez, reportedly a target for Real Madrid, left Anfield.
"You can't defend him," Fowler told Talksport. "I love him as a player, but you cannot condone what he's done."
David Usher, owner of fanzine The Liverpool Way, believes the club should stick with their troubled striker, adding: "He needs help and he may as well get it from Liverpool rather than somewhere else."
A number of companies involved with Suarez have already begun to question their relationship with the player.
Adidas is currently holding discussions in Brazil about their association with Suarez, while 888 Poker tweeted: "We are reviewing our relationship with him. We will not tolerate unsporting behaviour."
In Uruguay, Suarez trades on his bad-boy image, so his latest transgression could increase his marketability.
Creative chairman of advertising agency Green Cave People, Malcolm Green, told BBC Sport: "The level of social media interest shows he has been able to take his infamy to new heights in an instant.
"More than just a pantomime villain, he is now able to take the role to unprecedented heights."