Barton was given the ban by the FA after elbowing Carlos Tevez in the face and being shown his marching orders against Manchester City on the Premier League's final day, then compounding the misdemeanour by kneeing Sergio Aguero in the back and attempting to headbutt Vincent Kompany.
Keane told The Sun on Sunday: “The reality is that he [Barton] has become a liability for QPR.
“No manager expects to have a dressing room full of angels and you will allow players to get away with indiscretions if they deliver on the park.”
Keane also dismissed Barton’s apology and believes that it is not as simple as just letting him leave Loftus Road.
"I'm all for people getting second chances but how many chances does one person need?"
He added: “If you want people to forgive you, you don’t just say, ‘I’m sorry, like it or lump it’.
“It’s not like the first time he has stepped out of line but there’s no indication that he’s willing or able to change.
“I’m all for people getting second chances but how many chances does one person need? The thing is, it’s not as easy as saying QPR should get rid of him.
“He’s got three years to go on a contract worth £70,000 [per week]. Who is going to take him?
“QPR might have reckoned they were doing good business when they signed him on a Bosman transfer last summer — but there was a reason why Newcastle let him go on a free.
“He did OK at Newcastle but they came to the conclusion that they were better off without him and, as it turned out, it looks like they were.
“Do QPR decide to just take a hit of £11 million and let him go as well? That’s an awful lot of money to pour down the drain.
“If it turns out they are willing to take such a gigantic hit, Barton will know just how big a liability he has become.
“He might find someone else willing to give him another chance ... but he is going to run out of them pretty soon.”