The three-time former champion fired in three centuries in rapid succession to see off the threat of second-round opponent Mark Williams, rallying from 8-8 to win 13-10.
O'Sullivan vowed in a television interview to put a halt to any future interview when he is branded his "own harshest critic", but was nevertheless typically tough on himself.
The three-time champion took issue with a BBC interviewer's remarks, saying: "When you play poor snooker, you play poor snooker. I don't listen to people saying I'm my own harshest critic. You don't know what you're talking about."
Selby crushed Stephen Hendry 13-5 from 4-2 behind and will present another tough challenge for O'Sullivan.
Ali Carter and Shaun Murphy contest the first session of their quarter-final later today, which is when O'Sullivan and Selby also start. Carter saw off Joe Perry 13-11 yesterday, and Murphy beat Ding Junhui 13-10.
Scotland's Graeme Dott and Northern Ireland's Mark Allen begin their quarter-final today, as do Neil Robertson and 52-year-old Steve Davis.