The incident happened after Derry City lost 2-1 to Dundalk in an FAI Cup semi-final replay at Brandywell Stadium.
There are reports a Dundalk supporters' bus was vandalised during the trouble that happened outside the grounds.
Police have yet to confirm the incident.  Derry City have yet to comment.
Derry councillors have condemned the attack.
Councillor Gary Donnelly said a group of Dundalk fans were cornered by a gang of youths outside a pub on the Lecky Road.
"When I arrived the crowd had dispersed and the Dundalk fans' mini-bus, which had been attacked, had been repaired and they were about to leave the area but they were visibly shaken," he said.
Mr Donnelly told BBC Radio Foyle that the supporters' mini-bus had its tyres slashed and graffiti sprayed on windows.
"Residents told me that after the game a number of Dundalk fans were making their way back to the bus when one of them was assaulted.
"A young boy of about 14-years-old was hit on the back of the head with a bottle before locals intervened and the four guys ran off."
Sinn FÃ©in councillor Patricia Logue, who lives in the area, said extra security may now be needed during match nights.
"This is criminal behaviour by youths who are causing mayhem in our community," she said.
"The people of the Brandywell, the visiting fans, Derry City Football Club, do not want this happening in the area.
"The residents are distraught and extra security will be one of the topics I'll be talking about to the relevant agencies today."
A teenager suffered head injuries, not said to be serious, during trouble that followed a football match in Londonderry on Tuesday night.