John Higgins suffered a shock loss to world number 59 Robbie Williams in the first round of the German Masters in Berlin on Thursday.
The four-time world champion was beaten 5-4 despite roaring back from 2-0 down to lead 3-2 with breaks of 134, 88 and 138 - the highest three of the match by either player.
Williams responded to take the next two before a run of 74 from world number six Higgins levelled at 4-4, but the Liverpudlian edged a nervy decider.
Williams, who had never previously played Higgins, told World Snooker Tour: "I was lucky to win the end. That chance he had in the last frame you expect him to clear up under that pressure.
"I was very fortunate to get over the line, but I'm very pleased."
World number nine Ding Junhui also failed to progress as he surrendered a 4-2 lead to lose 5-4 to Scott Donaldson.
Shaun Murphy had no such problems, beating Tom Ford 5-1 and Neil Robertson overcame Ian Burns by the same scoreline.
World champion Judd Trump claimed his place in the quarter-finals as the second round got under way.
Luca Brecel enjoyed breaks of 102, 122 and 78 but it was not enough as he was beaten 5-3 by Trump, who did not register a century.
Graeme Dott, Matthew Selt and Michael Georgiou also won through to the last eight.