West Ham boss Gianfranco Zola described his shock after the Carling Cup second-round victory over Millwall was scarred by pitch invasions and ugly clashes between fans in and around Upton Park.
One man was stabbed in the chest near the stadium among the chaos, with a number of arrests made for disorder and breaches of banning orders.
Neil Harris had given the visitors the lead but Junior Stanislas' equaliser that sent the tie into extra-time sparked ugly scenes as supporters poured over the advertising hoardings.
Stanislas added another from the penalty spot, which saw more fans enter the pitch and led to Millwall players heading for the dressing room, before play got under way again and Zavon Hines added a third to seal victory at the end of a poisonous evening of hostility.
"I've been involved in difficult games and things happened. Here, I've played seven years and I've never seen it like this," Zola said.
"It's certainly not good for football. I was completely shocked. Totally.
"I knew it was a game that meant a lot for the two sets of supporters, but I didn't imagine it like this.
"What can I say? I'm a sport man. I love the game. I love to go on the pitch and try and make it exciting for the supporters and enjoyable for everybody to watch. This was beyond my powers."
The FA have vowed to investigate the violence between the rival fans.
Carlton Cole was the victim of monkey chants, before the England striker appeared to make a gesture back to Millwall fans.
"I didn't know he was abused by the supporters," Zola said.
Instead of talk being of Jack Collison bravely declaring himself ready to play despite his father dying in a motorcycle accident on Sunday, there were concerns at kick-off of the trouble that led to a Tube delay and empty seats.
Of Collison's situation, Zola added: "He showed what kind of boy he is by playing. Not many would have done the same thing."
Millwall boss Kenny Jackett added: "I didn't fear for my own safety."
He added: "There were no Millwall fans on the pitch. They stayed where they were supposed to.
"There were a lot of people on the pitch. The lads gathered together and came to the sides, as they should have.
"I wasn't aware of the stabbing outside the ground. I'm very sad to hear that. We've got a passionate game in this country, but when it oversteps the mark then things have to be done."