Chris Wakelin, the 13th seed, made it 12 out of 12 seeded players to advance, sealing a 10-6 victory over 20-year-old English qualifer Liam Pullen.
Wakelin had led 5-4 overnight but Pullen, the world number 86 who battled through four qualifying rounds to qualify, made it 5-5 – only for Wakelin to win five frames in a row.
“I’m gutted for Liam as he is a really good friend of mine – we practice a lot and he is an incredible player,” said 34-year-old Wakelin.
“A few years ago we first practiced together and he stuffed me and I thought ‘what a talent’. It’s a shame he didn’t fully show what he is capable of but he did really well and made a good account of himself.
“I’m really proud that he has been here for the first time and every single person in that arena wanted him to win, me included. But I’m here to win and sometimes you have to be ruthless.
“I watched the draw and I didn’t want to draw Stan [Moody] or Liam as they are my friends and I want them to win.”
Pullen, who lost his World Snooker Tour place last May, then regained it a few weeks later at Q School, said he loved his first Crucible match.
“I really enjoyed every moment,” said Pullen. “I felt at times I held my own and I thought it was a very tight 10-6. I loved it. You have got to have fun and I felt close to doing something but it didn’t quite click.”
In the afternoon session, O’Sullivan will be looking for a quick finish as he leads 7-2 against another debutant, China’s He Guoqiang, while Si Jiahui begins his match with Iran’s Hossein Vafaei.