The five-time winner marched on at the Crucible with a 13-7 victory over an opponent who had a match to forget.
Over the course of the contest, O'Sullivan fired two centuries and nine further breaks over 50, showing no sense of a hangover from the controversy he sparked with criticism of Barry Hearn and snooker's governing authorities last Sunday.
A satisfied O'Sullivan waved to the crowd as he strode on to a clash with either Ding Junhui or Liang Wenbo.
O'Sullivan said: "There might not be the intensity or the tournaments or the wins there were three or four years ago but I'm happier for it. I don't feel there's that much pressure on me any more.
"I'm really not that bothered. I know it might sound crazy.
"At the end of it, if I was to win it I'd be sitting here saying it was a great, great feeling, but I've had that feeling five times before.
"It's nice for a few days, a week or so, but after that you think, 'Is it worth putting 365 days of blood, sweat and tears into hopefully winning the world title, to get that feeling?'.
"I've never been driven by records and titles and being the greatest player on the planet.
"I don't see that I need to write a great album any more, I just need to be a supporting act. I don't mind letting the other guys write the good albums.
"I'm happy to just be invited along and have them bring me out for half an hour - 'Here he is, he's still alive, he can still perform' - but then I'm happy to fade back into the security of life."
Murphy was outspoken about O'Sullivan's spat with Hearn prior to the contest - and admitted he did not believe the former world No 1 didn't care about winning.
Murphy said: "I thought Ronnie played really, really well in the whole match and if he plays like that with that kind of focus I think he'll win.
"I don't subscribe to all this 'not being bothered' stuff he comes out with. He certainly looked like he was trying to me.
"If he turns up to his next match with that level of focus, then whoever he plays next is in trouble."
O'Sullivan played down Murphy's comments after reaching his 18th quarter-final at the Crucible.
"I don't really pay much attention to what anybody says," O'Sullivan said. "You just come here, get in your little cocoon and do what you have to do.
"It's a long slog, it's very hard mentally for me, and I know it is for everybody else.
"I'm like a band or a singer nowadays. But I'm not confident of writing great albums every year.
"I haven't had the greatest of seasons - I haven't written a great album this year - but it hasn't been a bad year."
Asked if he had become the Rolling Stones of the snooker circuit, O'Sullivan said: "The Rolling Stones are still the big act, they don't support anybody. Maybe I'm a bit like James Blunt. He seems a pretty cool dude."