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O'Sullivan was the quickest out of the blocks. His long potting was almost unerring throughout the evening, and it seemed to take Selby by surprise.
Ronnie O'Sullivan sinks brilliant long red to take opening frame
The Rocket went into the mid-session interval 3-1 up, wrapping up with a fine break of 85.
Selby was more in the game after that, though, punishing some of O'Sullivan's little mistakes - ending the evening by clearing the table after the 44-year-old missed a red to the green pocket that had seemed relatively routine.
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In the earlier semi-final, McGill won the first three frames, opening with a break of 83 and following with 78.
Wilson got on the board shortly before the mid-session interval but the Scot continued to dominate, putting on a break of 69 in the sixth frame to extend his lead.
Wilson showed no signs of the form that saw him dump defending champion Judd Trump out of the tournament 13-9 at the quarter-final stage.
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But McGill erred in the seventh frame, when he was looking set to clear the table to overcome a deficit of 45 - but he left himself an awkward angle on the blue, missing the pot and handing the advantage to his opponent instead. Wilson promptly cleared to get his second frame of the day.
Yet the 29-year-old stayed focused, sending in a break of 92 in the final frame of the afternoon to go in 6-2 ahead.