SHEFFIELD, England - Ronnie O'Sullivan made a triumphant return to snooker after a year away from the game with a 10-4 first-round win over Marcus Campbell as he opened the defence of his world crown on Saturday.

England's O'Sullivan has only played once competitively since lifting his fourth world title last May but showed no sign of being rusty as he raced to a 7-2 lead in the first session.

O'Sullivan took only 93 minutes of the evening session to wrap up the win over Scotland's world number 27 Campbell who is ranked one place higher due to his opponent's lack of matches.

O'Sullivan, 37, will face either Ali Carter, who he beat 18-11 in last year's final, or world championship debutant Ben Woollaston in the second round next Saturday at the Crucible.

"I was not sure how the match was going to go and not sure how I was going to compete, it was an experiment in some sorts of ways," O'Sullivan was quoted as saying by the BBC.

"In general I wasn't as slick or as tight as usual. But you've got to expect that if you've not played for a year, you can only get that through matches.... it's like trying to get fit for a marathon the day before a marathon starts."

O'Sullivan played once early in the campaign but announced in November that he would not feature again this season only to change his mind in February. This is his first tournament back.

Asked about O'Sullivan's chances of retaining his world title, Campbell said: "He could certainly go and win it and batter everybody but given the amount of quality players in the field I wouldn't be surprised if he lost."

The world championship continues to the final on May 6.