Emotional volatility, ranging from unbridled enthusiasm to despairing dejection, is not the only negative for Ronnie O'Sullivan in his latest quest to channel his unrivalled natural talents into the most tangible reward that snooker can provide - success at the 888.com World Championship. Aged 32, he no longer has time on his side.

When the sport's foremost championship was first contested at the Crucible in 1977, those in their early thirties were considered fresh-faced rookies. Now, even though it would be stretching a point to describe O'Sullivan as a veteran, he is rapidly approaching such status.

The cerebrally demanding 17-day potting-fest in Sheffield has often been described as a marathon of the mind and since 1986, when Joe Johnson stunned everyone - himself included - by winning the championship at the age of 33, no one of O'Sullivan's vintage has gone the distance.

Gone are the days when Fred Davis reached the semi-finals aged 64 in 1978, the year that Ray Reardon won the event for a sixth and last time at 45. Steve Davis captured his sixth world title in 1989 aged 31, Stephen Hendry's Crucible-record seventh triumph was achieved in 1999 when the Scot was 30 and John Higgins won his second title last year aged 31, nine years after winning his first.

Given his ability to intimidate by making snooker appear preposterously simple to master, O'Sullivan is the bookmakers' favourite, but for a well-rounded package of confidence, reliable temperament and mental equilibrium, Shaun Murphy, Stephen Maguire and Mark Selby stand out as the men to beat.

Murphy produced a Johnson-esque outcome by winning the 2005 World Championship as a qualifier. He remains a fearsome long potter, but having sought advice from many knowledgeable quarters, he has significantly upgraded his tactical armoury.

The 25-year-old will make the daily commute from his home in Rotherham as No1 in the provisional world rankings. Never one to doubt his place in the sport's highest echelon, Murphy has deeper self-belief than ever.

Much the same goes for Maguire, 27, who, since the crushing blow of losing 17-15 to John Higgins, from 14-10 up, in an epic Crucible semi-final last year, has won the Northern Ireland Trophy, the China Open, with a maximum break en route, and reached the Maplin UK Championship final.

Maguire is a formidable, levelheaded match player, but Mark Selby, 25, is a rock in the heat of battle, who compensates for a relative lack of flair with an attitude that, regardless of circumstances, remains in rude health. He blends the enthusiasm of an amateur with the savvy of a top-quality professional.

At 10am today, Higgins launches the championship against Matthew Stevens, twice a finalist since 2000. Last year, Graeme Dott's defence ended on the first day against Ian McCulloch and Higgins could well suffer an identical deflation.

One to watch

Mark Allen is immersed in snooker and possesses the talent and temperament to make a memorable impact on his second visit to the Crucible.

Last year, in only his second season as a professional, the Northern Irishman, an attacking left-hander, marked his Crucible debut by beating Ken Doherty, the 1997 world champion, 10-7 in the first round and has continued to improve while also gathering the necessary experience for a sustained challenge in Sheffield.

Allen’s first-round opponent tomorrow is Stephen Hendry, the most successful player of the modern era. However, the Scot’s confidence is unusually low after a fruitless season and he could be vulnerable to the youthful fearlessness of Allen, 22.

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