Ronnie O’Sullivan lost 4-3 to China’s Yan Bingtao in the third round of the Northern Ireland Open but defending champion Judd Trump progressed.
Trump won a final-frame decider to beat Jimmy Robertson 4-3 and make the quarter-finals at the Waterfront Hall.
The former world champion will face Mark Allen in the last eight on Friday.
Allen was 3-1 up on Scotland’s Stephen Maguire, who battled back to level before the Northern Irishman got over the line to triumph 4-3.
Antrim’s Allen will compete in the quarter-final stages of his home event for only the second time and for the first time in five attempts, having underperformed in Belfast recent years.
Earlier on Thursday, Allen had defeated four-time World Championship semi-finalist Matthew Stevens 4-1 to reach the third round.
Trump remains on course for a fourth consecutive Northern Ireland Open title – if successful, the world number one-in-waiting will become the first player to win a ranking event four times in a row since Stephen Hendry won a remarkable five successive World Championship crowns between 1992 and 1996.
O’Sullivan out after urging fans to ‘sit down’
O’Sullivan began his match against Yan brightly, edging 2-1 ahead with the help of a 129 break, but the Masters champion levelled to leave the score 2-2 before nudging one frame ahead.
A superb clearance of 73 saw six-time world champion O’Sullivan restore parity but his opponent rallied to claim the decisive seventh frame.
O’Sullivan urged spectators to “sit down” during the third frame, pausing midway through his century break to urge fans to keep their seats.
It capped a fractious week for O’Sullivan at the Waterfront Hall, having criticised the lack of atmosphere at the venue before feeling the need to clarify that his complaint had not been aimed at fans.
His complaint prompted the referee to instruct stewards not to let fans enter the auditorium mid-frame during the best-of-seven match.
Higgins earns comeback win over Williams
The 40th competitive meeting between John Higgins and Mark Williams was a dramatic affair as the Scot recovered from a 3-0 deficit to emerge a 4-3 victor.
Welshman Williams, who has been struggling with a bout of gout all week, built up a 54-21 advantage in frame four but a missed red allowed Higgins to compile a 42 clearance and claw his way back into the match.
A break of 110 in the next enabled the four-time world champion to reduce his arrears further and he went on to complete his comeback by grinding out victory in a tense decider.
Higgins will play the winner of the match between Mark Selby and David Gilbert on Friday, while Yan’s prize for defeating O’Sullivan is a contest with Mitchell Mann.
Shaun Murphy, 4-1 winner over Stuart Bingham, will take on Jackson Page or Ricky Walden, who prevailed 4-1 over Australia’s Neil Robertson in the second round.