Five people were arrested and a nine-year-old boy injured amid unsavoury scenes at Blackburn's Carabao Cup derby with Burnley.
There was a heavy police presence for the second-round clash between the East Lancashire neighbours, which ended in a 2-0 victory for Burnley at Ewood Park.
After Jack Cork put the visitors ahead in the 27th minute, two Blackburn fans ran onto the pitch, with one confronting a number of Burnley players.
The supporter was pictured with his hand on Ashley Westwood's throat before he was tackled to the ground by the Burnley midfielder.
Lancashire Police confirmed a man was arrested and is being held in police custody on suspicion of assault and pitch encroachment.
Meanwhile, a nine-year-old boy suffered minor burns after a flare thrown from among the Burnley fans towards the pitch landed on his back.
A man has been arrested in connection with that incident, while three other people were also arrested following other incidents in the ground.
Assistant Chief Constable Terry Woods said on www.lancashire.police.uk: "We expected and planned for a lively match, which is exactly what we got.
"Due to a significantly planned and resourced policing and club operation, there were no significant incidents of disorder amongst the large number of supporters. That said, a small number have yet again let the fans down.
"I am truly appalled at the behaviour of these few, including the one believed to be from the Blackburn fans who encroached the pitch and thought it acceptable to assault a steward doing his job and two players there to partake in the match.
"Just as despicable was the man who threw the flare that hit a child. Thankfully he wasn't too badly injured and was left with minor burns."
It was otherwise a good night for Burnley, who made it four wins in a row and seven games unbeaten against their bitter rivals in a game that reflected the current fortunes of both clubs.
Clarets boss Sean Dyche gave a debut off the bench to record signing Chris Wood, who arrived from Leeds on Monday in a deal that could be worth Â£17million.
Wood made an immediate impact and was twice denied by good saves from Rovers keeper David Raya.
The striker will hope to make a full debut against Tottenham on Sunday, while he can also prepare for a swift reunion with his old club after Burnley were drawn against Leeds in the third round next month.
Dyche said: " He's only been in a couple of days. I thought he delivered a good performance.
"He had a very strong chance, the lad makes a great save, and then second half he just catches one a bit too clean. But he'll learn how we play and get used to the players around him."
Wood came on before half-time for Jonathan Walters, who suffered an ankle injury on his first start for the club.
"He tried to play on, we gave him the benefit of the doubt, and it wasn't quite right," said Dyche. "We'll find out more over the next couple of days when it settles down."
While Burnley head to Wembley, Blackburn must prepare for a League One date with MK Dons.
Boss Tony Mowbray said: "We have to focus on the hard work, the competitive edge to try and win our fans back to the point where they believe this team can win football matches in League One and be successful this year."