Former world champion Mark Williams ended Yan Bingtao's reign at the Masters, with Neil Robertson also advancing.
Yan led at the interval as he looked to defend the crown he won last year, registering breaks of 64, 71, and 57 en-route to a 3-1 lead.
However, a remarkable one-handed fluke when attempting to escape a snooker in the fifth frame hauled Williams back into the match before he went on to claim the following three as well.
Yan responded with a sensational break of 122 to keep himself alive in the match, but Williams was too strong and eased himself over the line in relative comfort.
"It's just nice to be playing front of a crowd," Williams told the BBC.
"Back home we're still under (coronavirus) restrictions so to come here and play in front of this fantastic crowd is great. The arena is probably the best I've ever played in.
"I think it was a good game. I've been playing like that most of the season really, just been a bit unfortunate I had to miss a few events.
"There's nothing better than beating the defending champ anywhere, but here is even more special. The first time I won this he wasn't even born. Just to get to venues like this at my age is just brilliant."
Williams, who made five breaks over 50 and the first century of the tournament in frame eight, won the British Open in August last year but was forced to miss the European Masters and English Open after contracting Covid-19.
The veteran left-hander blamed the after-effects of the virus for falling asleep in his chair during his UK Championship match against Anthony Hamilton in November, but now looks to have made a full recovery.
"I'm all right as long as I haven't got to go up and down any stairs," Williams joked.
Australia's Neil Robertson also advanced to the quarter-finals with a 6-3 win over Anthony McGill in the evening session.
Breaks of 78 and 115 helped McGill establish a 2-1 lead before a rusty Robertson began to find some form, contributions of 75, 94, 57 and 62 giving the left-hander the hard-fought victory.
"It was tough," Robertson told Eurosport. "Probably too much of a break over Christmas for me. I only gave myself five good days for practice and certainly felt really, really rusty the first few frames."