However, even when McManus, the world No 6, levelled at 10-10, helped by two century breaks, Doherty never wavered. The two players, embroiled in a strangely scrappy encounter, discovered a little style after coming out of the final mid-session break.
Runs of 69 and 86 took the Ilford-based Dubliner back in front at 12-10. McManus, who had won their three previous meetings since February, secured frame 23 convincingly 122-0. But in a 47-minute 24th frame marathon, Doherty survived some nail-biting moments to win 68-42.
Doherty emulated the former UK Champion Patsy Fagan who reached the last eight in 1978 only to lose to Fred Davis. Doherty began the day 6-2 ahead, won the ninth on the pink and the 10th on the black but after that it was all downhill until 10-10. 'Neither of us played very well but at least I made a match of it,' said McManus whose defeat leaves Stephen Hendry to fly the Scottish standard once again. 'Maybe I could have won it but I never felt really happy.'
Doherty, who now meets Jimmy White or Neal Foulds, said: 'It would have been a tough one to lose after making all the pace. Alan's one of the toughest competitors you could wish to meet but we always seem to have close battles. Even though I'd lost the last three I took comfort from the fact I'd won in a couple of finals last year over the longer distance.'
Steve Davis, aiming to win a modern-day record seven world crowns, was steady rather than spectacular in opening up a 5-3 overnight lead over the world No 13 Steve James.
Nigel Bond will be looking for revenge when he tackles the injured Hendry for a second year running here on Tuesday. Bond, the world No 9, set up the meeting by defeating the Welshman Terry Griffiths 13-8 at the Crucible yesterday.
'I don't think I'll have any advantage over Stephen because of his injury,' said Bond, beaten 13-7 in the quarter-finals 12 months ago. 'He didn't play too badly with one good arm against Dave Harold and knocked in some good breaks.'
Hendry reported no overnight complications from his fractured left elbow when he returned to the Crucible for a brief practice and to watch his stablemate Doherty. 'The arm hasn't stiffened noticeably and I enjoyed a good night's sleep,' said the relieved title holder, who on Friday absorbed the pain to defeat Dave Harold 13-2 with a session to spare.
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