Former champion Mark Selby survived a comeback to beat Sam Baird 13-11 and reach the quarter-finals of the World Championship.
2014 winner Selby made fluent breaks of 134, 133 and 115 to go 11-7 ahead, but Baird pulled back to 11-11 before Selby took the two he needed.
Two-time finalist Ali Carter suffered a surprise 13-11 defeat by Alan McManus in the second round.
Welshman Mark Williams beat Michael Holt 13-8 to go through.
Two-time champion Williams will play Judd Trump or Ding Junhui on his first appearance in the last eight since 2011.
Ronnie O'Sullivan trails Barry Hawkins 5-3 after the first session of their second-round match.
Although five-time winner O'Sullivan made a stunning 139 break in only eight minutes in the second frame, Hawkins won the last two.
Four-time champion John Higgins opened up a 5-3 lead over Ricky Walden, the Scot making a century break in the final frame of the session.
Both matches resume on Sunday at 14:30 BST.
Selby survives super Sam onslaught
There was only one frame between world number 59 Baird and Selby until 6-6, before the world number one pulled away with some heavy scoring.
However, Baird rallied and fought back to go just 11-10 behind, before winning a drawn-out 22nd frame which lasted 48 minutes. But Selby's resilience and experience saw him through.
"I never take anything for granted and make every match difficult for myself," said Selby, who faces Mark Allen or Kyren Wilson next.
"My safety was very poor throughout the match. Sam played great and put me under pressure.
"From 11-17 to 11-11 I was missing pots I wouldn't usually have done. At that point, I would have put him favourite.
"My concentration seems to be wandering all the time. I am over the moon to still be here."
Twenty-seven-year-old Baird, playing only his third match at the Crucible, was visibly shattered after a late finish.
"It is all a blur. The last session was so mentally draining," he said.
"I have never been so exhausted after a game of snooker. Every time I got to the table it was so difficult."
The revival of veteran McManus
Scot McManus has reached the quarter-finals in Sheffield five times in 20 appearances since his debut in 1991, making the semi-finals twice.
He failed to qualify between 2007 and 2012 but will face Walden or Higgins in the last eight.
"I got the ideal start on Saturday having been 9-7 down," said 45-year-old McManus, the oldest player left in the tournament.
"I won a frame on the black ball and relaxed after that. I wanted to be 10-10 but 11-9 ahead was huge for me.
"I still practise a lot and work hard at the game. I enjoy it. Sometimes I am out there looking around and think 'I might not be here again - it is a special place to be'."