Ronnie O'Sullivan was left visibly frustrated during his World Snooker Championship clash against John Higgins . The seven-time World Champion was taking on Higgins in the last-16 encounter at the Crucible Theatre, Sheffield, with a quarter-final berth on the line. O'Sullivan had stormed into a 6-2 lead heading into the evening session, but watched his advantage whittled down to three frames as Higgins clawed it back to 9-6 going into the final frame of the night. As O'Sullivan attempted a red