SUNDERLAND have confirmed they have launched an internal disciplinary process following footage of Darron Gibson's foul-mouth criticism of a number of his team-mates on Saturday night.

Gibson, seemingly under the influence of alcohol, was filmed after the Black Cats’ 5-0 hammering by Celtic at the Stadium of Light when he was in conversation with a group of supporters.

The Republic of Ireland international was recorded as he delivered verdicts on the commitment levels of some in the dressing room and the overall state of the club, after he had been criticised for being in a bar at the Ramside Hall after such a defeat.

Sunderland manager Simon Grayson has spoken to him and Gibson has said sorry for his actions, which have brought unnecessary extra pressure on the squad and club with Friday’s season opener with Derby County approaching.

The statement read: “Darron Gibson has not conducted himself in a manner befitting Sunderland Football Club. As a consequence, we will initiate our internal disciplinary process to deal with the matter. Darron has apologised this morning.”

There are no suggestions from Sunderland over what punishment could be handed to him, but the situation is clearly an unwanted distraction ahead of a new season in the Championship following last season’s relegation from the Premier League.

But they are understandably annoyed by his behaviour, which included threatening one Sunderland fan who questioned his performance and why he appeared to have been drinking alcohol after losing to Celtic.

The 29-year-old was filmed saying ‘we’re f*****g s**t’. He was then asked if that bothered him, and he replied: “Of course I am (bothered). I don’t want to be s**t. There are too many people at the club who don’t give a ****.”

The bust-up with the fans continued when he was asked to explain who he was referring to. After saying ‘you tell me’ he appeared to suggest Lamine Kone, Wahbi Khazri and Jeremain Lens were among those not pulling their weight.

When the Sunderland fan suggested Gibson’s drinking after such a heavy defeat didn’t present a committed picture of himself either, he said: “Right, I might be off my face in here but I still want to play for Sunderland. The rest of them f*****g don’t though.”

Gibson made 12 Premier League appearances after moving from Everton last season and still has one year remaining on the 18-month deal he signed in January.

Grayson has inherited him after taking over the managerial reins from David Moyes and Gibson was a second half substitute during the defeat to Celtic.

The Sunderland manager is still looking to make further changes to his squad and he has been weighing up which players to move on.

Lens was one of those questioned by the Sunderland fans during the verbal exchange with Gibson and the Dutch winger could leave before the end of the week.

The Holland international is understood to have agreed terms with Besiktas and the two clubs are still in discussions over the transfer fee.

Sunderland have rejected an offer from Besiktas already and hope to receive around the £8m mark. He was left out of the squad to face Celtic over fears he could suffer an injury that could prevent a deal from taking place.

A deal for Lens would help Grayson’s pursuit of Aston Villa striker Ross McCormack. He can leave Villa Park and Sunderland have tried to take him on loan because Steve Bruce would prefer to do a permanent deal.

Bruce, who didn’t take the Scotland striker on a trip to Germany, said: “There’s been an enquiry. I don’t know. There’s been enquiries from a couple of clubs, that might happen in the next week or so, we’ll wait and see.”