Snooker World Championship: With the form book thinner than usual after a season featuring only five ranking events plus the Masters, innate class seems the most reliable indicator of what will transpire at the Crucible in the next 17 days.

If Ronnie O'Sullivan were a horse, his record of three first-fence falls and a non-start in his last four ranking races would discourage most punters but he has come away from the Crucible with the title twice in the last four years and in January, in a Masters final of the highest quality, lost only 10-9 on the final black to John Higgins, the only player to win more than one title in the current campaign.

In trouncing O'Sullivan 9-2 in October's Grand Prix final, Higgins set two records, centuries in four consecutive frames and 494 unanswered points, and he might well have acquired two other titles on the road to Sheffield instead of suffering 9-8 defeats to Ken Doherty and Mark Williams respectively in the finals of the Malta Cup and China Open.

So far, Higgins has been the player of the season but the 1998 champion faces a prospective second-round match against Williams and, according to the seedings, a quarter-final against O'Sullivan.

Williams burnt out mentally for a while shortly after winning his first world title in 2000 and did so again not long after securing his second in 2003.

Unable to summon much appetite for practice, his results deteriorated so alarmingly that six months ago he was contemplating relegation from the top 16.

Eventually, his survival instinct reasserted itself, his desire to practise returned and the China Open gave him his first title for 29 months.

The class was always there - last year he made a 147 at the Crucible - but the consistency was not.

Unlike Higgins and Williams, O'Sullivan has become, as he has privately admitted, ring-rusty. His 5-1 defeat by Ian McCulloch in the Welsh Open and his 5-0 drubbing by James Wattana in Beijing are the only matches he has played in 11 weeks.

Nevertheless, the Crucible's longer matches, starting at best of 19, and as kind a draw as any title contender could hope for, should enable him to pick up form and momentum for a quarter-final against either Williams or Higgins.

The other prospective semi-finalist in this half, Stephen Hendry, has taken little pleasure in regaining top place in the provisional world rankings as it is 14 months since he last won a title.

The seven-time champion's break-making remains as classy as ever - he made four centuries in six frames in the Malta Cup - but at the age of 36 top-level consistency has eluded him in his quest for an eighth world title.

In the top quarter, Shaun Murphy does not have the easiest of starts to his title defence today against the experienced Wattana.

Murphy has reached only one final in his year as champion, losing to Stephen Lee for the Welsh Open title, and may feel more pressure defending the title than he did during last year's adventure as a 150-1 outsider, but the other seeds in his quarter are all veterans.

Steve Davis's hopes of a last hurrah at the Crucible at the age of 48 were resurrected by a discovery about sighting and alignment which helped carry him to the UK final in December although he has achieved nothing of note since Christmas; Jimmy White, 44 next month, needs to win his opening match against one of his regular sparring partners, David Gray, to be sure of finishing the season in the top 32; Peter Ebdon has done little this season to suggest a repetition of his 2002 triumph.

Steven Maguire cannot go on playing as poorly as he has throughout a season he started as the world number three; Matthew Stevens, who has reached two finals and three semis at the Crucible in the last six years, has won only one ranking match in a season he started at fourth.

Nevertheless, the likely semi-finalist from this second quarter is Ken Doherty, winner of the Malta Cup, who in reaching three Crucible finals, winning in 1997, has proved that he has the requisite class and staying power.

Weekend Order of Play

Today

10am - S Murphy (Eng) v J Wattana (Tha); G Dott (Sco) v J Parrott (Eng).

2.30pm - S Davis (Eng) v A Hicks (Eng); J Higgins (Sco) v M Selby (Eng).

7pm - S Murphy (Eng) v J Wattana (Tha); S Lee (Eng) v A Carter (Eng).

Tomorrow

10am - K Doherty (Ire) v B Hawkins (Eng); G Dott (Sco) v J Parrott (Eng).

2.30pm - S Maguire (Sco) v M King (Eng); S Lee (Eng) v A Carter (Eng).

7pm - S Davis (Eng) v A Hicks (Eng); J Higgins (Sco) v M Selby (Eng).

Monday

10am - K Doherty (Ire) v B Hawkins (Eng); P Hunter (Eng) v N Robertson Aus).

2.30pm - S Maguire (Sco) v M King (Eng); M Williams (Wal) v A Hamilton (Eng).

7pm - M Stevens (Wal) v J Swail (NIrl); P Hunter (Eng) v N Robertson (Aus).