Tottenham Hotspur midfielder Eric Dier was involved in a confrontation with a fan after his side's penalty shootout defeat by Norwich City in the fifth-round of the FA Cup on Wednesday.
The England international, who scored his spot-kick in the shootout after the match ended 1-1, appeared to be upset at something said after the game and climbed into the crowd.
Video footage showed Dier climbing over seats and confronting a home fan before he was restrained by security guards and other fans. He was eventually led away.
It is believed his brother was in the section where the incident happened and Dier could be heard saying "he's my brother" in video footage posted on social media.
Tottenham manager Jose Mourinho said he had sympathy for Dier but said his actions were wrong.
"I think Eric did what we professionals cannot do but probably every one of us would do," he told reporters after his side's fourth successive defeat.
"When someone insults you and your family is involved, especially your younger brother.
"This person insulted Eric, the younger brother was not happy with the situation and Eric was not happy. But we as professionals cannot do what he did.
"But I repeat, probably everyone of us would do," he said, adding "I am with the player and I understand the player."
It is not the first time a player has clashed with a fan this season. Arsenal's Granit Xhaka was stripped of the club captaincy after mouthing an expletive to home fans when substituted in a match against Crystal Palace.
Dier's action is potentially more serious though and could lead to disciplinary action.
It is another worry for Mourinho whose Tottenham side are unravelling after an initial revival when the Portuguese replaced Mauricio Pochettino.
Their run of defeats includes a 1-0 home loss to RB Leipzig in the Champions League, defeat away to Chelsea and a home loss to Wolverhampton Wanderers at the weekend that left Tottenham in seventh place in the Premier League.
With his leading strikers Harry Kane and Son Heung-min still missing with injuries, Tottenham are fully stretched and Mourinho again said some of his players were exhausted.
"I am not going to say what everybody knows so this time I am not going to say that but I have to say Steven Bergwijn, it's too much for him to play so many minutes like he is doing," Mourinho said, "I prefer to call Lucas (Moura) a hero, he is playing every minute of every game in every position.
"Harry Winks was completely dead. I think he's started 11-12 games in a row, we had many many players in trouble."
(Reporting by Martyn Herman, editing by Ed Osmond & Shri Navaratnam)
