London: Reigning world champion Ronnie O`Sullivan is concerned the years are against him as he bid to equal Stephen Hendry`s modern-day record of seven global titles.
The 38-year-old O`Sullivan, a five-time world champion, begins his quest on Saturday for a third straight triumph after winning the World Championship in 2012 and 2013.
Since the tournament moved to the Crucible Theatre in Sheffield, northern England, in 1977 only Steve Davis and Hendry have won three successive world titles.
O`Sullivan, who begins his latest title defence against Finland`s Robin Hull, is keen to make the most of his relative youth as he believes it is unlikely he will win multiple world titles in his 40s.
"I`m not saying it can`t happen because you never know. But I don`t want to put unrealistic targets on myself, or unnecessary pressure. I want to be happy with what I`ve achieved while striving to win another," O`Sullivan told Eurosport.
"I can`t expect to win another three going into my 40s when nobody has won more than one beyond the age of 31 over the past 40 years, apart from me and John Higgins.
"It would be stupid of me to set myself high targets that nobody has achieved in the history of the sport. For me, it is about enjoying as many World Championships as I can play in.
"I think you would have to equal Hendry`s record to be classified as the greatest of all time. I can`t put myself in that league just yet. I`m happy that I`ve won it five times over a 13-year period."
The Englishman, nicknamed the `Rocket`, added: "To be the greatest, I think anyone would have to win seven. I`d like to win one in my 40s. But to win two or three from now, is asking a lot of myself."
O`Sullivan arrives at the Crucible in good form, having won the Masters in January and the Welsh Open with a maximum 147 break in March. Ding Junhui, looking to become the first Chinese player to take the title, has already won five ranking titles this season to match a record set by Hendry in 1990/91.
Ding faces qualifier Michael Wasley on Sunday.
Meanwhile Australia`s Neil Robertson, world champion in 2010, is up against Crucible debutant Robbie Williams.
Four-time champion John Higgins faces Alan McManus in an all-Scottish clash, 2011 runner-up Judd Trump plays Tom Ford while last year`s losing finalist Barry Hawkins has been drawn against fellow Englishman David Gilbert.
Six-time former world champion Davis, together with fellow ex-winners Mark Williams and Graeme Dott, as well as 2002 champion Peter Ebdon, have all failed to qualify. Ireland`s Ken Doherty, the 1997 world champion, is the oldest man in the first round draw at the age of 44.