• Defending world champion went to A&E with chest pains • Neil Robertson into last eight with 13-6 win over Shaun Murphy

Defending world champion Mark Williams has revealed doctors are confident his health scare is not related to his heart after going to hospital suffering from chest pains.

The Welshman lost the opening session of his second-round match with David Gilbert 5-3 at the World Championship in Sheffield. Later, Williams posted on Twitter that he was in the A&E department of a local hospital, saying: “Couldn’t stick the chest pains no more.”

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The 44-year-old informed tournament officials of the issue after the session and was advised by the on-call doctor to attend hospital. Williams made his own way there and is understood to be with his wife Joanne and son Kian.

Williams posted an encouraging update during Friday evening. “Doctors are confident it’s not anything to do with my heart,” he tweeted. “Awaiting more tests at 10 o clock. #cantwaitformebed.”

Breaks of 105, 66 and 58 had earlier helped Williams get back on level terms against Gilbert, but the latter took the last two frames of the day to carve out a 5-3 lead. Their last-16 match is due to resume at 10am on Saturday at the Crucible.

Meanwhile Australia’s Neil Robertson has become the first player to reach the quarter-finals after beating Shaun Murphy 13-6 in the second round. Robertson led 5-3 after the opening session and took the second by the same margin to open up a 10-6 lead before Friday’s final session.

The 2010 champion snatched the first frame of the day with a break of 67 and continued to score more heavily than Murphy, who managed a highest break of 59 in the session, but won two hard-fought frames to trail 8-6. Murphy missed a difficult brown in the 15th frame and his opponent took full advantage to clear the colours.

Robertson won the final frame of the session as well and finished the match off in style when the players returned for the evening session. The world No 4 rattled in breaks of 143, 88 and 95 to justify his position as tournament favourite following Ronnie O’Sullivan’s shock defeat at the hands of James Cahill.

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Cahill was also in action on day seven and had to fight hard to stay in touch with Scotland’s Stephen Maguire, who ended their opening session with a two-frame advantage. Aided by breaks of 67, 103, 56, 61 and 125, the two-time semi-finalist Maguire led 2-0 and 5-2 but Cahill dug deep. The score at the end of the second session was 9-7 to Maguire.

The three-time champion Mark Selby faces a battle to reach the last eight as he trails Gary Wilson 9-7 overnight. Wilson took the day’s last three frames with breaks of 97, 115 and 78.