Nice guy swimming in shark pool. Despite what people may think, Fergal O'Brien doesn't wear the sign on his back.

Cursed with being dubbed "The Affable Irishman", O'Brien's burden at the Crucible this year is to prove that at the table he is as prepared as anyone to splatter a little blood and bite an opponent when he's going under, just like the best of them.

As O'Brien was steadily crafting frames for a 3-1 mid-session lead against sixth seed Stephen Lee, before going into a 5-3 overnight lead, Dominic Dale of Wales was throttling the conqueror of Ronnie O'Sullivan, David Gray, 13-1 in a breathless entrance to the quarter-finals of this World Championship. That scoreline hasn't been seen since 1991.

If O'Brien, who took over eight hours to dispose of Chris Small in the first round, is to seriously contemplate winning the second big tournament of his career, having won last year's British Open, the Dubliner may well have to borrow some of Dale's ferocity.

Ruthlessness is a facet of Ken Doherty's genetic construction that must express itself as he prepares to meet Anthony Hamilton this afternoon. The only other Irish player in the competition, Belfast's Joe Swail, faces up to John Parrott over the long weekend.

While O'Brien's 25-frame match will finish tonight - assuming it goes to three sessions - Swail and Doherty are scheduled to end on Monday.

Given that Doherty has gotten over his beloved Manchester United's shattered European dream, Hamilton should prove to be a doughty opponent but unlikely winner.

O'Brien opened by losing the first frame yesterday afternoon to Lee before knocking in a session-high 86 break. Skirmishing well and taking advantage when he was allowed, he went into the mid session break 3-1 ahead.

Lee responded, drawing the match back to 3-3, with the sixth frame lasting a draining 36 minutes. Another marathon followed, but O'Brien won the seventh in 35 minutes and did well to scramble the last one too, with a highest break of 34.

With champion Stephen Hendry and Ronnie O'Sullivan long forgotten, Ireland's best hope, Doherty, might well advance as far as the final stages. Still, next season's world number one, Mark Williams and the current number one John Higgins are in his side of the draw.

Possible? Of course. As the 1998 World Champion well knows: with United losing at Old Trafford and George Best going off the drink, anything is.