|Betfred World Championship|
|Venue: Crucible Theatre, Sheffield Dates: 31 July-16 August|
|Coverage: Watch live on BBC One, BBC Two, BBC Four and Red Button, with uninterrupted coverage on BBC iPlayer, BBC Sport website and BBC Sport app. Full details and times.|
Ronnie O'Sullivan saw his overnight lead disappear as three-time winner Mark Selby hit back to lead their World Championship semi-final 9-7.
Selby, who beat O'Sullivan in the 2014 final, trailed 5-3 after the first session but took four frames in a row.
Five-time champion O'Sullivan responded with two of the next three, but Selby's 76 break gave him a two-frame lead.
England's Kyren Wilson is closing in on his first world final, fighting back to lead Scotland's Anthony McGill 13-11.
Trailing 6-2 overnight, Wilson responded on Thursday by drawing level in the second session at 8-8 then taking the lead in the third.
Wilson, who beat 2019 champion Judd Trump in the previous round, needs just four more frames to reach his maiden final at the Crucible Theatre, with this semi-final concluding on Friday from 14:30 BST.
Meanwhile, fans will be allowed into the arena this weekend for the showpiece.
O'Sullivan's frustrations come to the fore
Despite difficult playing conditions on Wednesday owing to humidity, O'Sullivan settled better and opened up a 5-2 lead against fellow Englishman Selby.
'The Rocket' had a 51-point lead in the eighth, but Selby recovered to take the frame and that started his revival in the match.
A notably fierce competitor, Selby started Thursday's session by taking a prolonged opening frame and followed it up with breaks of 97 and 58 to lead for the first time in the match.
O'Sullivan, appearing in the last four at the Crucible for the first time since being beaten by Selby in the final six years ago, made contributions of 87 and 82 in between Selby's 62.
An all-important final frame of the session saw O'Sullivan in among the reds only to miss a long-range pink into the green pocket that left him punching the table in frustration as he went back to his seat.
In contrast, Selby kept himself together with a fine break to grab a two-frame lead heading into the third session on Friday at 10:00 BST.
O'Sullivan hurting - analysis
Six-time world champion Steve Davis:
Selby will be delighted with that session, he has turned it around. A frustrating session for Ronnie O'Sullivan and he missed a pink in the final frame which we would have expected him to get. That [punching the table] must have hurt his knuckles.
The next session is very important, it is an early morning start on Friday and Ronnie needs to be out of the blocks pretty quickly. A Mark Selby in the right frame of mind is tough to reel in.
1997 world champion Ken Doherty on BBC Two:
A tense afternoon and you can see how much it meant to Ronnie. Where he let Selby off the hook last night, he was completely different in his approach in today's final frame. He knew he had his opponent and he was keeping his foot firmly on him.
That was a great break and it will hurt Ronnie, he didn't play well today and that will have been brought on from last night when he did not finish the session well.
Ronnie will need to win the third session 5-3, if he loses it he will be well behind going into the final session.
Wilson turns it around
Qualifier McGill started the match strongly by taking a 6-2 lead, but Wilson fought back in superb fashion with two centuries and three further breaks of 70 or more to level at 8-8.
During the second session, Wilson's onslaught meant McGill was restricted to potting just 47 balls in the eight frames.
The first four frames in the third session were shared, including Wilson compiling 99, but the Kettering man took charge thereafter.
He made 116 to lead for the first time in the match at 11-10, as well as taking the next two which included his fourth ton of the contest.
But despite being outplayed for much of the day, McGill managed to stay in touch at just a two-frame deficit by compiling a stunning 136 clearance in the 24th frame.
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