Ryan Day admits he is at a loss to explain his performance after surrendering nine frames in a row to crash out of the World Snooker Championship in Sheffield.

The Pontycymer potter led Mark Allen 3-1 at the Crucible Theatre before the Northern Irishman responded in style to win their first-round clash 10-3 and end the Welshman’s season.

Day has pedigree at the Crucible, having reached the World Championship quarter-finals on three previous occasions, but played well below that level against Allen.

And the 35-year-old concedes that losing concentration at crucial moments cost him in a sub-par display.

“I was feeling good in the match at 3-1 going into the mid-session interval and then I don’t know what happened after that,” said Day.

“I switched off a bit, lost a bit of focus and lost a lot of frames I should have won in the second mini-session.

“It was difficult to take missing chance after chance in the afternoon – I’ve won games from 6-3 down before but tonight things didn’t really happen.

“Things then didn’t go my way in the evening session and Mark started playing like I know he can.

“I guess I’ll have a holiday and a bit of time off now but the new season starts in May so it won’t be long before I’m back playing.”

Meanwhile, Matthew Stevens established a healthy advantage over Mark Williams in their all-Welsh first-round clash.

In a repeat of the 2000 World Championship final, won 18-16 by Williams, Stevens scored consistently heavily to lead 7-2.

A scrappy opening frame was eventually claimed by Ebbw Vale-born potter Williams but his 37-year-old opponent then reeled off three on the trot, including fluent breaks of 111 and 96.

The gap was narrowed to 3-2 but Stevens continued to make light of his 21-place ranking deficit with a gritty 51 break to restore the two-frame advantage.

And following a 36-minute seventh frame it was the world No.35, three years younger than Williams, who pinched it on the black. And Stevens also won the next two final frames of the opening session and needs three more for victory.

The pair will play to a finish from 2:30pm on Wednesday, with a potential second-round contest against five-time world champion Ronnie O’Sullivan on the line, and the winner will be Wales’ sole representative left in the tournament.

Mark Williams (right) during his match against Matthew Stevens (left), during the Betfred World Championships at the Crucible Theatre, Sheffield

O'Sullivan could be set for a fine after playing with no shoes on for some of his 2015 opener against qualifier Craig Steadman on Tuesday.

In terms of the scoreline, five-time champion O'Sullivan enjoyed a relatively comfortable time of it, emerging from the first session of the encounter - that had begun with him making a century break - with a 7-2 lead over Crucible debutant Steadman.

But the world number two, who suffered a broken ankle towards the end of last year, appeared in discomfort due to his footwear at one point and opted to remove his shoes, briefly playing on in his socks.

He subsequently borrowed a pair of shoes from tournament director Mike Ganley and put them on, but Press Association Sport understands the World Professional Billiards and Snooker Association will look into the matter to consider whether it constitutes a breach of its rules about members' dress code, which could see O'Sullivan handed a fine.

Meanwhile, two-time finalist Ali Carter, given the all-clear from lung cancer in December, made a winning start to his campaign as he completed a 10-5 win over veteran Scot Alan McManus.

Carter finished the job from a 6-3 overnight lead to set up a last-16 meeting with Australia's 2010 champion Neil Robertson, the world number four.

"I didn't feel as if I played great, but I competed in all departments and won quite convincingly in the end," Carter told a press conference.

"I have some good memories here - the only thing I have left to do is win it, and that's what I'm here to do."

Earlier, world number three Ding Junhui overcame the embarrassment of missing out on a maximum break after forgetting he was on track for a 147 to book his place in the second round.

China's Ding was trailing opponent Mark Davis 5-3 and was at the table on a break of 96 when he inexplicably screwed back for the blue ball instead of playing for the black.

The apparent lapse in concentration left the audience stunned, while Ding covered his head in his hands then proceeded to smile after realising his error.

Following his mistake, Ding regained his composure and went on to claim a 10-7 win over Davis.

Ding admitted he did not realise he had been on course for a maximum break until the crowd gasped after the shot which put him on the blue.

"I didn't even know about the 147," Ding said.

"I potted the red and heard the noises from the crowd and I realised what I had done. The blue was on its spot and I was just trying to make a century, I wasn't even thinking about making the 147. "

Ding will play John Higgins in the next round, and added: "I've played him many, many times. I've learned a lot from him. I've got more confidence to play him now."

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