Ronnie O’Sullivan is in danger of falling victim to one of the biggest shocks in Crucible history as he trails amateur James Cahill 5-4 in their World Championship first-round match.
Cahill, 23, settled immediately against the world number one to go 1-0 up.
He then trailed the five-time champion 2-1, 3-2 and 4-3, but came back on each occasion and pinched frame nine.
Cahill needs five more frames for victory when the match resumes at 10:00 BST on Tuesday.
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Debutant qualifier Cahill, the first amateur to play at the Crucible, showed great resilience to stay in the match when many would have crumbled.
A confident start saw him win the opening frame with a brilliant pot on the black.
The 43-year-old 36-time ranking event winner responded, pouncing on Cahill mistakes to go 2-1 ahead with breaks of 51 and 86.
Cahill kept his composure with a fine 71 to level at the mid-session interval and the pair then exchanged frames.
O’Sullivan’s performance was becoming increasingly error-strewn and he was fortunate to fluke a snooker and steal frame seven, but Cahill once again showed his backbone, winning two tense frames for a first-session lead.
Meanwhile, four-time champion John Higgins beat Mark Davis 10-7 to progress.
Scotland’s Higgins was in impressive form to see off his fellow veteran in an intriguing match.
Six-time world champion Steve Davis on BBC TV
It was probably the worst session of snooker Ronnie O’Sullivan has played this season.
I just think he is playing too quickly. It’s as if he wanted to get out of there. It didn’t look like he was enjoying being there.
James Cahill’s attitude has been brilliant. He has played with rhythm and confidence.
Higgins holds off Davis fightback
Last year’s runner-up Higgins fended off a spirited effort from the 46-year-old Davis to reach the second round.
Higgins, making his 25th consecutive Crucible appearance, led 6-3 overnight only for his advantage to be cut to 7-6.
But two superb tons helped him get to within one frame of the victory target and he closed out the win in frame 17.
“I was really happy with the first session and to be 6-3 in front,” said Higgins. “I felt really focused.
“But the pressure began to hit a little bit and Mark came back really strongly and I was thinking it would get away from me. I think I was lucky to win the game because Mark let me off the hook a few times.
“I was missing some unforgivable balls but I made a good break after the interval and then a good break to go 9-7 so I am pleased with that.”
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