STEPHEN Hendry, the seven-time world champion, believes Ronnie O'Sullivan will have to "knuckle down" if he is to stand any chance of eclipsing his impressive record of world titles.

Hendry remains the most successful player on snooker's greatest stage and has won an unprecedented 36 ranking titles but the all-conquering Scot has acknowledged that the "Rocket" has the potential to win three more world crowns having made his green baize comeback after a 12-month sabbatical.

"If he [O'Sullivan] has got ambitions to beat my record, he really needs to knuckle down," said Hendry. "He just has to have one objective over the next few years.

"He has got the game, but whether he has got it in him to focus and dedicate his life we will have to see. If Ronnie plays to his potential, well he's the favourite to win the World Championship.

"He has got the talent, no doubt, but Ronnie can be unpredictable when it comes to pulling out of tournaments and saying he wants to quit and then coming back."

Defending champion O'Sullivan showed few signs of rustiness or nerves in easing to a routine 10-4 first round win over Scot Marcus Campbell in Sheffield at the weekend. It is a victory which has enabled the four-time world champion to take his first step towards joining an elite group of players who have won the world title five or more times.

Only Hendry and Davis – who has six world crowns – have won more titles than O'Sullivan at the Crucible, while Ray Reardon is the only other player to have won six world titles in his career. And while Hendry knows that O'Sullivan could beat his record one day, he is still happy to see the Englishman back competing again.

"It was very important Ronnie came back because he is the best player in game," added Hendry. "It is like saying Tiger Woods is not going to play golf any more. It just wouldn't be the same."

Former Crucible winner Graeme Dott returns today with a healthy 6-2 lead over Peter Ebdon in a match which conjures memories of their 2006 world final, which the Scot won. The world No.11 fought hard for his four-frame cushion, but the pair's match was suspended a frame early because there were fears it would affect the start of the afternoon matches.

Dott pocketed breaks of 60, 55, 52 and 70 to leave Ebdon with a real fight on his hands to stay in the tournament.

Four-time world champion John Higgins will have to come back from behind to keep his Crucible hopes alive. The Wishaw man trails Hastings' Mark Davis, who beat him at the UK Championship earlier in the season, 6-3 after the opening session of their best-of-19 frame showdown.

Ricky Walden, the former Shanghai Masters champion, avoided a third successive first-round defeat with a dominant 10-1 victory over Nottingham cueman Michael Holt.

Chester's Walden led 8-1 overnight and needed just 40 minutes to win the two frames he needed for a last-16 place.

Breaks of 76, 55, 78, 46, 61 and 140 – the highest of the tournament so far – did the damage as Walden prevailed.

Mark Williams, the two-time world champion, suffered a surprise 10-6 defeat to Michael White, one of six players who are making their Crucible debuts this year.