The club were forced to act after midfielder Gibson was caught on video admitting he was “off his face” before verbally attacking his team-mates when talking to fans in a bar on Wearside.
The Republic of Ireland midfielder was also heard saying: “We’re s**t. Of course I’m bothered, I don’t want to be s**t.”
The 29-year-old received criticism from fans who blasted him for being intoxicated just six days before the start of the season.
In a statement released by the club this afternoon, Gibson was referred to as ‘Darren’ rather than ‘Darron’. However, his name is spelt correctly further on in the piece.