Northern Ireland's Joe Swail and Anthony Hamilton could not be separated after the penultimate session of their second-round meeting in the World Snooker Championships at the Crucible today.
And another close finish is in prospect tonight after Nottingham-based Hamilton recovered from 6-3 down to level at 8-8.
Swail, who defeated Dubliner Ken Doherty in his first match, made a half century in each of his frame successes with a best of 98.
In contrast, Hamilton, responsible for the demise of six-times world champion Steve Davis, compiled just two runs of 54 and 63.
They play a possible nine frames tonight with a place against the volatile Ronnie O'Sullivan in the quarter-finals at stake.
Earlier today reigning champion Mark Williams was beaten 13-11 in his second round encounter by Joe Perry, despite staging a strong comeback in the final session.
Williams, 10-6 down when play resumed, reeled off five frames in a row to edge in front.
However, Perry regained his composure with three half-century breaks in as many frames to seal a shock victory over the world number one.
"It's been a bad season for me," said the 29-year-old Welshman. "I wouldn't put myself in the same league as Ronnie O'Sullivan and Stephen Hendry, the way I've been playing."
Perry could not contain his joy after upsetting the odds. "This is the biggest win of my career," said Perry. "To beat the world number one and reigning world champion at the Crucible is fantastic. It shows I can beat anyone on my day."
Perry will now face Matthew Stevens in the quarter-finals after the Welshman beat close friend Paul Hunter 13-12.