By Mark Orlovac
BBC Sport at the Crucible
Doherty is bidding for his second world title
Ken Doherty booked his place in the last eight after claiming an epic 13-12 victory over a stubborn Graeme Dott.
Doherty had been 2-7 down but after pulling back to 7-9 on Sunday night, he won the first four frames of the final session to lead 11-9 at the interval.
The game descended into a war of attrition but Dott dug in and won three of the next four frames to set up a dramatic finale.
Doherty then hung on in a 42-minute decider to claim an unconvincing win.
I'm thrilled to win but hopefully I can play better - I will have to if I am going to win this tournament
Afterwards, the former world champion admitted that the gruelling win had taken its toll.
"I'm absolutely shattered - it was a marathon and not pretty to watch but there was a lot of tension," he said of the nine-hour contest.
"You are never beaten, in the last frame you just need half a chance and anything can happen.
"I'm thrilled to win but hopefully I can play better - I will have to if I am going to win this tournament."
Graeme Dott expressed his disappointment after the dramatic contest.
"When the score was 12-12, I thought I was the stronger player. If I got a chance in the final frame I would have won but I could not get in," he said.
"Going 6-2 up at the start can be deceiving as you are nowhere near the end and keeping a lead is hard.
"At a few points people thought I would be easily beaten so I think I've proved a lot of people wrong."
Second round result: K Doherty (Irl) 13-12 G Dott (Sco)
27-61, 25-59, 36-59, 72-60, 7-96 (58), 0-98 (67), 0-80 (80), 68-23, 8-59, 76-10, 92-0, 56-55, 84-0 (68), 69-32, 50-72, 18-80 (80), 68-66 (Doherty 50, Dott 52), 75-30 (62), 62-32, 69-41, 41-59, 64-1 (50), 8-66, 1-90 (59), 62-30.