Mark Allen became the third seeded player to fall at the first round stage of the World Championship following a 10-8 defeat to Mark King on Monday night.
Northern Irishman Allen, ranked No 6 in the world, saw an 8-6 lead slip from his grasp as left-hander King roared back to advance to the second round for the seventh time in his career.
The defeat sees Allen follow fellow title contenders Mark Williams and John Higgins out of the exit door at the famous Crucible venue.
King's reward is a last 16 meeting with either Ding Junhui or Alan McManus.
Last year's runner-up Ali Carter came from behind to edge 5-4 ahead of fellow Englishman Ben Woollaston, who made a decent impression on his debut. They play to a finish on Tuesday night.
A surprise result was in the offing as Thailand's world number 70 Dechawat Poomjaeng moved 5-3 ahead of Glasgow's Stephen Maguire, a semi-finalist last year.
Graeme Dott won the battle of former world champions as he saw off Peter Ebdon 10-6, with the Scot edging through a tense battle that went to an unscheduled third session, finishing off with a century break to ensure Scotland will have at least one representative in the last 16.