There was no question that Ronnie O'Sullivan was irritated with his own play and it appeared that he was also frustrated with his opponent.
The way Mark Selby was drinking his water got to the Rocket, who stopped and had a word with the match referee about it.
After the referee went over and had a word with Selby about his behaviour while sitting in his chair, O'Sullivan proceeded to miss a straightforward pot.
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It seemed as though O'Sullivan had allowed the moment to get to him and Selby ended up taking a commanding lead into the interval between sessions.
O'Sullivan complains to referee about Selby then misses red
"What's going on here?" Eurosport commentator Neal Foulds asked.
Well there is an argument that he has put himself off there I think!
Andy Goldstein described the incident as 'atergate' in the Eurosport studio and Jimmy White did not understand what the issue was from O'Sullivan's perspective.
It has been a testy encounter so far with the pair having a very bizarre few minutes at the end of the fourth frame when both played on with an irrelevant pink and black.
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Eurosport commentators David Hendon and Neal Foulds made it very clear what they thought of the incident which preceded the mid-session interval.
"The frame is over and Mark Selby is going to make his point by playing at the black," Hendon said on commentary.
It's all part of the little bit of spice that is in this match. It's a strange end. You can't get snookers on the black, it's just a fact!
Foulds took over: "Well, the frame is over. This is ridiculous. There is no more playing on now. There is nothing more to see."
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