Northern Ireland's Mark Allen was beaten 10-8 by Mark King in the first round of the World Championship in Sheffield.
The Antrim player lost the first two frames but recovered to lead 3-2 and then 4-3, before losing the final two frames of the first session.
In the final session, Allen went 8-6 ahead, but King hit back by winning four frames on the trot to advance.
Allen, a World semi-finalist in 2009, also lost in the first round last year.
The world number six, who retained his World Open title in March, made an unconvincing start against King, who is making his 14th appearance at the Crucible.
After going 2-0 down, the 27-year-old won the third frame comfortably with the help of a break of 83, the highest of the first session.
Allen restored parity after a run of 66 and the pair then won two frames apiece, King levelling at 4-4 with a break of 74 before winning the ninth to take a one-frame advantage into their second session.
Allen levelled by taking the first frame of the evening session and then fought back from 45 points to win the 11th by producing a 68 clearance to lead 6-5.
King, 39, looked certain to get on terms again in the 12th as Allen required three snookers but the Northern Irishman fought back to snatch the frame and take a 7-5 lead in what looked like a devastating blow for the Englishman.
To his credit, King - ranked 30 in the world - fought back to win the final frame before the mid-session interval, helped by a run of 44.
Allen restored a two-frame lead as a 31 clearance ended a marathon 14th frame but the dogged King showed real character to level at 8-8 after breaks of 74 and 89.
King took the last two and faces China's Ding Junhui or Scot Alan McManus at the last-16 stage.