Stuart Bingham won four frames in a row to defeat former world champion Peter Ebdon 10-8 in their first-round match at the Crucible in Sheffield.
The unfortunate Ebdon suffered a heavy contact during a crucial moment of what turned out to be the final frame.
Matthew Stevens won the last frame of the opening session of his match against Mark Allen to lead 5-4.
Former world champion Graeme Dott holds a healthy 6-3 advantage over Mark King in their first-round match.
Dott won four frames in a row to build a 6-2 lead before King hit a break of 69 to take the final frame.
Marco Fu leads Martin Gould 6-3, while Ricky Walden and Rory McLeod are tied at 4-4 in a see-saw contest.
Bingham at one point trailed 8-6 but mounted a strong fightback and held his nerve to close out a tight contest against the 2002 world champion.
Ebdon, making his 20th consecutive Crucible appearance, appeared well placed to level the scores at 9-9 and take the match to a deciding frame but he missed a crucial black.
Hong Kong's Fu lost in the first round to Gould in 2010 but fired breaks of 70, 97, 81, 63, 115 and 56 as he built a healthy lead.
At one point the 33-year-old was on course to equal the 137 made by Mark Williams, which currently stands as the highest break of the tournament, but ran out of position on 115 and missed the final brown.
That match finishes on Wednesday, with the winner set to play Neil Robertson's conqueror Judd Trump in the second round.
The match between McLeod and Walden is also scheduled to finish on Wednesday.
The English pair only managed eight of their scheduled nine frames in their session due to slow play, with the scores locked at 4-4.