Simon Grayson says Darron Gibson has admitted to being "bang out of order" and that Sunderland have dealt with the situation, adding that it's time to now move on.
Speaking for the first time about the incident in which the midfielder criticised several team-mates, the Black Cats boss admitted "it wasn't a very good thing to do."
Footage filmed in a bar on Saturday night, showing Gibson accusing colleagues of not trying hard enough, was put out on Twitter in the aftermath of the 5-0 home friendly defeat to Celtic.
"I think it's been acknowledged that it wasn't a very good thing to do," Grayson told BBC 5 Live. "The club have dealt with it internally.
"We've decided on the plan of action and that's deal with it internally.
"Players should be more responsible in this day and age.
"Social media plays a massive part in football, people are there to wind people up and make you say things you shouldn't say.
"Darron Gibson has admitted it and apologised that he was bang out of order, it has been dealt with.
"It is something that we didn't need leading up to the start of the season.
"Unfortunately, it happened and we dealt with it and we can look forward to the start of the season now."
Grayson said he would never go down the line of making any players go and train with the Under 23 club or train alone, even if they did not fit into his plans.
Some managers do take that course of action and remove individuals from the first-team squad, but the new Black Cats boss insists that's not his way.
But he added that those squad who were not fully committed could leave though said that none had taken him up on his offer.
"I need to call on all the players who are at my disposal," said the 47-year-old who only wants players with the right characteristics.
"There are players who will leave in the next few days and weeks while the window is still open and new ones will come in.
"The ones we bring in are going to have to be the right types, with hunger and desire.
"I've said to the players that if anyone doesn't want to be at the football club my door is open and I'll drive you to wherever you want to go to.
"I want players who want to play for this football club."