Davis shows his fighting spirit but is one frame away from elimination

Davis was on the brink of making a painful exit from the Betfred.com World Championship, trailing 12-4 to the man who has made a cruel habit of humiliating him on his favourite stage.

Robertson looked set to go through with a session to spare but still needs one more frame after Davis battled to take the last two of the evening to postpone what is surely an inevitable defeat.

The 52-year-old brought this tournament to life and won himself a new generation of supporters with his remarkable second-round victory against defending champion John Higgins.

It was tempting, and romantic, to believe amid the euphoria and the scale of his achievement that Davis might have rediscovered the form to take him all the way to the final, 21 years after the last of his six world titles.

But Davis warned he would be taking each ball and each frame as they came, rather than looking further ahead.

And in Robertson he met a player who potted ball after ball, winning frame after frame.

The 28-year-old from Melbourne showed Davis no mercy in the first round last year and repeated the treatment.

Davis gave another sell-out Crucible crowd a classic century to savour in the evening session, an immaculate 128, but that was out of keeping with the flow of the match.

Robertson raced into a 7-1 lead in the morning session and converted that into his emphatic overnight lead.

The evening interval score of 10-2 had a familiar look, given that Robertson crushed Davis by the same margin 12 months ago.

Mark Selby let Ronnie O'Sullivan off the hook as an intriguing first session between two of snooker's most potent potters finished all square.

The quarter-final was expected to be a thriller following the superb Masters final which the pair contested in January, but it did not begin in the manner of that Wembley match, which Selby won 10-9 from 9-6 down.

O'Sullivan had been majestic in the concluding session to his match against Mark Williams on Monday, making three centuries and giving the impression he was finally enjoying his stay in Sheffield, only to then offer a depressing assessment of his chances.

O'Sullivan finished off with a break of 81 to draw level at 4-4, but his potting was as unpredictable as his behaviour, and Selby was also far from his best.

At one stage in frame three O'Sullivan sat in the front row with journalists while Selby played a shot, to the amusement of the audience, and then he left his seat to watch events on the other table for several minutes, peering around the curtain to check on Ali Carter and Shaun Murphy.

The match O'Sullivan was taking such an interest in showed a 5-3 lead for Murphy after the opening session.

In the other quarter-final Northern Ireland's Mark Allen leads Graeme Dott of Scotland 5-3.