Anthony McGill held his nerve to sink Ronnie O'Sullivan in a final frame decider at the Crucible and banish any lingering memories of last year's semi-final nightmare.

McGill withstood a stunning comeback from the defending champion who turned a 10-5 deficit into an 11-10 lead, only for the Scot to battle back and clinch a place in the World Championship's last eight with a nerveless 85 clearance.

His 13-12 triumph came in startling contrast to McGill's previous final-frame decider at the famous venue when he had lost out to Kyren Wilson in arguably the most remarkable frame in the sport's history.

Out-of-sorts O'Sullivan had been outplayed in the second session by McGill, who won the first four frames of the day and finished a thoroughly composed afternoon session with a 10-6 lead over the defending champion.

Two centuries underpinned a near-nerveless performance from the 30-year-old, while in complete contrast O'Sullivan had laboured, and his decision to employ Mark Williams' controversial break-off tactic appeared to emphasise just how short he was on ideas.

Consecutive breaks of 47, 126 and 89 took McGill's remarkable streak to seven frames in succession, and a further 15 consolidated his advantage, but O'Sullivan managed to dredge up the final frame of the session with a quick-fire break of 69, and that would prove a springboard for a not entirely unexpected resurgence.

Not for the first time in his illustrious career, O'Sullivan returned a completely different proposition, digging out a staggering red to the middle despite being badly hampered by the jaws of the top pocket as he reduced his deficit to 10-7.

An equally brilliant green to the middle served up a break of 97 for 10-8, and as McGill began to wilt, O'Sullivan seized the advantage by wresting the next two frames and hauling himself back level in the match.

McGill returned from the mid-session interval clearly intent on trying to take the game to the champion, and despite O'Sullivan regaining the lead largely due to a break of 49, there were encouraging signs that the Scot was stirring.

His attitude paid off in the next when he capitalised on a poor O'Sullivan safety shot with a break of 87 to pull the match back level at 11-11.

After O'Sullivan had nudged back in front, McGill summoned a magnificent 136, his third century of the match, to force the decider.

O'Sullivan got in first with a break of 42 but a missed red left a chance for McGill, who cleared to win the match with an uncharacteristic roar.

Elsewhere on Friday,

Neil Robertson leads Jack Lisowski 9-7 after a high-quality session which saw the pair compile at least one half-century between them in every one of the eight frames they contested.

And Mark Williams scored two centuries as he overturned an early 3-1 deficit to establish a 5-3 overnight lead against John Higgins.