Liverpool forward Mohamed Salah said if he speaks "there will be fire" after he argued with manager Jurgen Klopp on the touchline during the 2-2 Premier League draw at West Ham.
Salah seemed to clash with Klopp as he prepared to come on as a 79th-minute substitute.
Klopp said he would not disclose what the argument was about, but former Liverpool striker Peter Crouch said on TNT Sports that "it doesn't look good for the club".
"Salah is a player who has started the majority of games for Liverpool and he will be fuming to be on the bench," Crouch said.
"But no one likes to see this between a manager and a key player."
Salah seemed frustrated at something Klopp said to him as he was about to be brought on, and seemed to want to prolong the altercation before team-mates Darwin Nunez and Joe Gomez shepherded him away.
The result left Liverpool all but out of the title race. They are third in the table and must rely on Arsenal and Manchester City dropping points to give them a glimmer of hope.
In a video on social media, Salah, as he was walking through the media area after the match, said: "If I speak there will be fire."
A reporter asked "Fire?" and Salah replied: "Yes, of course."
Klopp said later: "We spoke about that in the dressing room and it's done for me."
Klopp will leave at the end of the season and Liverpool this week agreed compensation worth up to £9.4m with Feyenoord for their manager Arne Slot.
There has also been speculation over the future of Salah, who has scored 210 goals in 346 appearances in seven years at Liverpool but whose contract expires at the end of next season.
He was linked with a move to Saudi Arabia last season and those rumours have begun to circulate once again.
Former Rangers striker Ally McCoist told TNT Sports: "He has been one of the best players we have seen in this league - nothing short of fantastic for Liverpool - but his form has dipped and it looks to me like he might be moving.
"It might suit both parties - suit Salah to move on and Liverpool to reinvest the money they get for him."
Salah has scored 24 goals in 41 games for Liverpool in all competitions this season.
Former Liverpool defender Stephen Warnock told BBC Radio 5 Live that the argument was a "clash of egos".
"You have two people who are equally important to the football club," he said.
"The connection between the two has to be of respect and respect how they have helped each other's careers.
"With Mo Salah being pushed out a little bit, he doesn't like that."
