Swindon manager Paolo Di Canio had a bust-up with one of his own players on the pitch after their Carling Cup loss to Southampton.
Leon Clarke first rowed with a fitness coach, before Di Canio stepped in and asked the striker to leave the field.
Swindon chairman Jeremy Wray said Clarke refused, and the pair then became involved in a physical row.
The dispute continued down the tunnel, and afterwards Clarke, 26, went back on to the pitch in protest.
Wray said he had launched an investigation into the incident intially involving Clarke and fitness coach Claudio Donatelli.
He told BBC Wiltshire: "Leon and the fitness coach were having words after the game.
"I think Leon felt he had given his all and his legs were heavy because he had been given an awful lot of running to do.
"The fitness coach's view was that he had done well and that was because of the training. It seems trivial but that argument has blown up.
"Paolo was concerned these discussions should be held behind closed doors and went to him to get him into the dressing room but Leon didn't want to go down."
Manager and player were then seen in a physical confrontation in the tunnel area.
Wray said he couldn't comment about what "went off in the tunnel" until he had obtained all the facts.
The chairman went back onto the pitch to speak to Clarke who he said was "shocked and angry".
"I checked whether he was going down the tunnel to shower and change but he left separately," he said.
"He should've come off the pitch when asked to by the manager.
"Clearly it wasn't dealt with in the right way."