MARK Allen edged 9-7 ahead in his last-16 meeting with John Higgins in a tight encounter between the pair.
The pair had shared the eight frames of the opening session on Saturday, but, after an even start, back-to-back wins in the 11th and 12th frames put Higgins 7-5 in front.
However, number four seed Allen then took control by winning the next four frames on the bounce – which included a 94 break – to lead by two.
Stuart Bingham fended off Jack Lisowski’s comeback to also take a 9-7 lead into Monday’s session.
Bingham extended his lead to 6-3 after taking the ninth frame, but Lisowski responded by taking the next three to claw his way back into contention.
However, Bingham finished strongly to take a two-frame advantage into the final session.
Stephen Maguire completed a 13-9 win over Shaun Murphy to reach the last eight, where he will face David Gilbert. The other quarter-final already decided will see Judd Trump take on Jak Jones.