O'Sullivan continued his successful return to the big stage with another victory over the player he beat in the final last year to win his fourth Crucible crown. Carter looked the stronger player when he came from 5-1 down to 7-7, putting O'Sullivan under pressure he has not experienced over the past 12 months.
But Chigwell's 37-year-old O'Sullivan responded in terrific style by winning six of the last seven frames to set up a quarter-final with another Essex cueman, Stuart Bingham. Among the balls he is as fluent as ever and he is now rated favourite to win the £250,000 top prize and become the first player to win back-to-back world titles since Stephen Hendry reigned supreme from 1992-96.
The first frame tonight was a tense affair lasting 28 minutes and it came down to a safety battle on the last red. O'Sullivan converted a brilliant double the length of the table and cleared to the pink to lead 10-7. German Masters champion Carter took the next with a run of 86 but he barely got a chance in the next three frames as O'Sullivan displayed wonderful fluency in breaks of 88, 106 and 89 to cruise over the winning line.
"It was another tough match and I was just pleased to have got through," said the Rocket. "Anyone who says they're never uncomfortable out there is lying. Even last year there were quite a few times during the tournament where I thought it was slipping away from me but you just have to stick in there.
"You've got to realise it's not a sprint it's a marathon and things can turn around at any point. You have to believe that you've got the ability if things do turn around, and stamp your authority on the frame. You have to stay with it and not get too worried when someone comes back at you.
"To have won the two matches that I've won and still be in the tournament is a bonus so to get another opportunity to play in a best of 25 at the Crucible is fantastic.
"I feel more burnt out now than I did last year. Last year the game was coming so easy to me that I could've played another 17 days after winning. I understand why people are saying it but I only believe burnout comes when the game becomes difficult.
"If the game is easy and you find your fluency, I don't really believe burnout can happen. I played 15 or 16 tournaments coming into the World last year and felt fresher than ever but I've had a year out and I've come to Sheffield and feel like I've played a mammoth season. I feel like I've just got off the plane from China."
Carter, who has still never beaten O'Sullivan in a ranking event, said: "When he plays like that every time I play him, there's no wonder I haven't beaten him. A lot of things happen out there that people don't see. Every time he goes into the reds he lands perfect on a ball, any little flick that can go wrong never goes wrong. But when you're playing well, that's what happens.
"I had him bang under it at 7-7. I shouldn't have taken on a long red, I should have perhaps played safe. But I was there to win, not to avoid defeat. If I could've got my nose in front who knows how he would've responded. It was a tough day today and he didn't do a lot wrong.
"If his head doesn't fall off then I think he'll win it. We all know if his head falls off that anyone can beat him. When he's playing like today then no-one can beat him. It makes no difference at all that he's been out for a year because he's been practising just like all the rest of us."
