World number one Judd Trump suffered a shock first-round defeat at the PTC Grand Finals in Galway as Alfie Burden sprung a huge surprise, while Ken Doherty also made a disappointing early exit.
A 4-3 victory saw Burden, a lowly 55 in the rankings, reach the last 16 of a full ranking event for only the second time in his career and the first since 1997.
Trump, who followed world number two Mark Selby out of the tournament, mustered a best break of 44 and made a number of mistakes around the table, while 36-year-old Burden impressed with breaks of 76 and, in the deciding seventh, 116.
And in the day's final game, Norwegian Kurt Maflin beat former world champion Ken Doherty 4-2. Much to the diosappointment of the home crowd.
"I should have won 4-2 but I haven't been in the big arena for a few years so I let the pressure get to me," said Burden.
"I thought I'd missed my chance so I was delighted to win it in one visit in the last frame. I beat John Higgins earlier in the season and in my book he's a better player than Judd, but in front of a packed crowd, to beat the world number one I'm over the moon."
Higgins may be rated highly by Burden, but the four-time world champion was knocked out 4-2 by a fit-again Ali Carter.
Carter, who could not take part in last month's Haikou World Open due to complications with his Crohn's disease, sealed a place in the last 16 with the win.
He took advantage of a missed red to make a 79 clearance in the first frame before Higgins made it 1-1 with a run of 111.
Carter then made it 3-1 and 4-2 to progress.
"I've been really struggling with my Crohn's disease and haven't been able to practise much so it's a big win for me," said Carter.
"I just dug in today and it was a good performance. The first frame was massive, it's hard to clear up from 60 behind, especially against John Higgins."
Chinese number one Ding Junhui reversed 3-1 deficit to defeat Andrew Higginson 4-3.
Higginson, a semi-finalist here last year, reeled off breaks of 57 and 71 on his way to a two-frame lead but Ding changed the momentum irreversibly with a turn of 118 in the fifth.
"I didn't play well for the first few frames, I found it difficult to control the white. After that I came back nicely," said Ding.
"I've been playing okay for the last few months so I'm happy at the moment."
His compatriot Xiao Guodong was also successful, securing a 4-1 win over former world champion Graeme Dott, who was in ragged form.
Rod Lawler denied China another winner on the night as he defeated Cao Yupeng 4-2.
After losing the opening frame, Liverpudlian Lawler took the next three to put him on the road to victory.