Darron Gibson: Sunderland midfielder faces action over video criticising team-mates
Sunderland have confirmed Darron Gibson will face an internal disciplinary process after he was filmed appearing to criticise team-mates after Saturday's 5-0 friendly loss to Celtic.
Midfielder Gibson, 29, has been at Sunderland since joining from Everton in January, making 12 appearances.
"Darron Gibson has not conducted himself in a manner befitting Sunderland AFC," a club statement said.
"We will initiate our internal disciplinary process."
The statement added: "Darron has apologised this (Monday) morning."
In the video, which was filmed in a bar by supporters and posted on social media, the Republic of Ireland international described the team as "s***".
He also claimed certain team-mates "did not care" about playing for Sunderland, but maintained he was committed to the club.
Sunderland, who were relegated from the Premier League last season, begin the 2017-18 Championship campaign with a home game against Derby County on Friday.