Ronnie O'Sullivan has felt 'wronged' by Ali Carter, according to former Scottish snooker star Alan McManus.
McManus claims O'Sullivan took Carter 'under his wing' when they were younger and is not happy with how he has treated him.
The latest instalment in an ongoing feud came in Sunday's Masters final at Alexandra Palace.
O'Sullivan came from behind to beat Carter 10-7 to win a record-extending eighth title.
Ronnie O'Sullivan beat Ali Carter in the Masters final
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Carter fumed afterwards that O'Sullivan had 'snotted' on the floor, while also calling out 'morons' in the crowd who were supporting the Rocket.
O'Sullivan was made aware of the comments at his post-match press conference, letting loose at Carter with an extraordinary expletive-laden rant.
McManus was at Ally Pally and had a close view of the tensions between the pair.
The pundit, who retired from playing in 2021, believes O'Sullivan feels he deserves more from Carter after they had 'grown up together'.
McManus said on ITV 4: "Well tensions were running high, it's a very hot atmosphere in Ally Pally.
"Myself and Ken [Doherty] were obviously there.
"Tensions can boil over, there is history between the two, they've kind of grown up together.
"Ronnie I think took Ali under his wing in some way a number of years ago and he felt a bit wronged on both sides of it.
"But it shows the importance and the tension that's going on at these big events."
World Snooker are reviewing O'Sullivan's rant, which included a middle-finger salute.
The pair first clashed at the World Championship in 2018, when O'Sullivan delivered a shoulder barge on Carter.
Former world champion Ken Doherty admits there is 'bad blood' between them.
He said: "There's history behind it, the shoulder barge at the World Championship, it goes from there.
"It's bad blood, I think he was reacting to what Ali had said in the press conference as well.
"I'm sure World Snooker will review it and we'll see what happens. Not great headlines really."
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Ronnie O'Sullivan and Ali Carter 'grew up together' before their feud exploded
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O'Sullivan claimed ahead of Sunday's final that Carter was a 'nightmare' to play against.
And he reiterated his opinion in fiery post-match comments.
O'Sullivan said: "[Carter] needs to sort his f*****g life out.
"I'm not going to skirt around it anymore, tip-toeing on eggshells around someone like that. He's a f*****g nightmare.
"Playing snooker against someone like that is a nightmare.
"He's not a nice person. It's not a nice vibe he leaves around the table.
Ronnie O'Sullivan launched a blistering attack on Ali Carter after his triumph at the Masters
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"I've said my piece, I don't give a s**t. I've said it now, done. You know what he's like, everybody knows what he's like.
"He's got issues. F*****g why has he got issues with me? I'm not having it.
"I don't care, grow some balls. I don't give a f**k about any of these snooker players, any of them.
"The more he brings it on, the more I f*****g punish him every time.
"He's just digging a grave for himself. I don't give a f**k. That's it, I've said my piece."