Ronnie O'Sullivan came through his first test of the Betfred World Championship but struggled to show his best form.
A 10-3 victory over Craig Steadman, whose Crucible debut was a constant struggle, asked more questions than it answered about O'Sullivan's form.
A handsome winning margin disguised what was a mediocre opening performance from the five-time champion, who was wearing a comfortable old pair of dress shoes for the finale to the contest, having risked a fine by briefly playing in his socks when a new pair were causing him pain on Tuesday.
It is understood O'Sullivan could face a small punishment, in the region of £250, for being in breach of the World Professional Billiards and Snooker Association's dress code.
"I got a pair of Mike Ganley's stinky old shoes, and you know what - they felt great"
He told BBC Two after clinching his last-16 place: "I've got no fashion sense at all. I had the last ones for 10 years - I didn't want to get rid of them and then I left them in a hotel and I lost them.
"I had this old battered pair, and I thought, 'I've got to buy a new pair', and I just bought the wrong pair basically.
"They were bashing my feet and I had to take them off. I couldn't wear them."
O'Sullivan borrowed shoes from tournament director Mike Ganley, who had warned him he required suitable footwear.
"He said, 'You cant play in your socks', but I didn't want to play in my shoes either," O'Sullivan said.
"I got a pair of Mike Ganley's stinky old shoes, and you know what - they felt great."
O'Sullivan began the two-session match with a break of 104, and added runs of 61, 59, 54 and 75 in establishing a 7-2 overnight lead, before doing enough in a scrappy morning session on Wednesday to cross the winning line and set up a shot at Matthew Stevens in the second round.
However many chances O'Sullivan needed to win his frames, Steadman invariably obliged, with a string of missed blacks on Tuesday proving highly damaging. A more composed opponent would have punished O'Sullivan.
The first frame of Wednesday morning went O'Sullivan's way, as Steadman's missing ways persisted. It seemed the pattern would continue into the next too when Steadman missed brown for the frame.
However the 32-year-old from Manchester had an unexpected reprieve when O'Sullivan overcut what looked a quite straightforward shot on the same ball, and this time Steadman made it count.
It was snooker from amateur hour at times, even from O'Sullivan, looking way off the game that has taken him to the last three World Championship finals.
As the mistakes from both men continued, O'Sullivan had a highest break of 27 to nudge 9-3 ahead, and snaffled the next to safely clear his first hurdle in the tournament.
Cambridgeshire cueman Joe Perry went close to beating O'Sullivan in the last 16 last year, and looked like easing through his first test this time after firing breaks of 94 and 87 in building an 8-1 lead over Chinese qualifier Zhang Anda.
Stevens set up a clash with O'Sullivan by completing a surprising 10-2 win over fellow Welshman and good friend Williams.
It was Williams who won the all-Welsh duel in the 2000 final, coming from 14-10 behind, but this time Stevens was dominant and after building a 7-2 lead on Tuesday night he returned to fire in 115, 45 and 73 to swiftly wrap up his win.
Stevens said on BBC Two: "I've had a lot of success here and a lot of disappointments from being ahead, which was going through my head today and quite a lot last night.
"But I felt in control today and it might be a sign of good things."
He knows O'Sullivan will provide a searching test though, with Stevens saying: "I'm not going to lie to you, I'm second favourite. I'm not expected to win but who knows. If I can play well hopefully I'll give him a good game."
Shaun Murphy, the 2005 world champion and current Masters title holder, looked sharp and made a top break of 101 in developing a 7-2 overnight lead over Finland's Robin Hull.
Judd Trump marched into a 7-2 overnight lead against Stuart Carrington, the 2011 finalist taking control in his first outing at the Crucible this year.
Trump now needs just three more frames to seal victory.
