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 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 becoming involved in a fracas before he was restrained by security guards.
It is believed his brother was in the section where the incident happened.
“When someone insults you and your family is there and your family gets involved with somebody who is insulting you, in this case a younger brother, I think Eric did what we professionals cannot do but, I repeat, probably everyone of us would do,” manager Jose Mourinho told reporters.
“This person insulted Eric, the younger brother was not happy with the situation, and Eric was not happy.
“We as professionals cannot do what he did.”
Mourinho did not want Tottenham to punish Dier for his actions, adding: “If the club disciplines Eric Dier, I would not agree with it. But what he did was wrong.”
Eric Dier just came into the stand and had a fight with fan next to me 😱 pic.twitter.com/nMGVcDWegX— Jascha Selby (@jselby123) March 4, 2020
Man City advance after Spurs crash out
Meanwhile, Manchester City won a 20th consecutive domestic cup tie to move into the quarter-finals with a 1-0 win at Sheffield Wednesday.
Sergio Aguero scored the only goal for the holders eight minutes into the second half as Wednesday goalkeeper Joe Wildsmith failed to get a strong enough hand to the Argentine's low strike.
A solitary goal was scant reward for the dominance of Pep Guardiola's men as the Catalan was rewarded for naming a strong line-up against the Championship side.
Riyad Mahrez and Gabriel Jesus missed glorious first half chances, while Nicolas Otamendi and Benjamin Mendy hit the woodwork before Aguero finally made the breakthrough.
City will travel to Newcastle in the quarter-finals.
Norwich will host Derby or Manchester United in their first quarter-final since 1992 after seeing off Spurs 3-2 on penalties after a 1-1 draw.
A bad night for Tottenham, who have now lost their last four games in all competitions, was compounded by the Dier incident.
Jan Vertonghen headed Tottenham into an early lead, but Mourinho's decision to hand 36-year-old goalkeeper Michel Vorm his first appearance of the season backfired.
The Dutchman spilled a long-range effort from Kenny McLean and Josip Drmic bundled home the rebound to level.
Both sides then tired badly in extra-time, but neither could find a winner and saves from Tim Krul to deny Troy Parrott and Gedson Fernandes allied to Erik Lamela's wild attempt that flew over the bar saw another shot at a trophy for Spurs slip by.
Eric Dier tryna fight a fan after a game🤨 straight savage 🙅🏼♂️ pic.twitter.com/CTiHVxsTU5— Jay Ilori (@JayIlori) March 4, 2020