Four-time champion Mark Selby is on the brink of crashing out of the World Championship at the first hurdle after losing the first session of his first round match 7-3 to debutant Joe O’Connor.

Selby, who questioned his future in the sport after losing to Gary Wilson in the Tour Championship earlier this month, was second best against his Leicester rival, who reeled off five frames in a row to leave himself in a commanding position ahead of Monday’s resumption.

The 40-year-old Selby has endured a dismal season by his standards, reaching one ranking tournament final and two semi-finals, but has traditionally reserved his best form of the season for the Crucible.

Despite sharing the opening two frames, Selby looked distinctly out of sorts and two centuries in three frames sent O’Connor three frames clear, before two further half-centuries sealed a sensational debut performance from the 28-year-old.

O’Connor, who has previously tried and failed seven times to reach the Crucible, is the only debutant in this year’s field, and requires just one more century on Monday to equal the record for a first-time performer at the venue.

Eleventh seed Zhang Anda followed defending champion Luca Brecel out of the tournament as he was hammered 10-4 by last year’s surprise quarter-finalist Jak Jones.

Resuming 5-2 in front after their abridged opening session on Saturday, Jones chiselled his way over the line with a top break of 60, while Zhang’s 95 in the 13th frame proved much too little, too late.

Jones, who beat Neil Robertson last year en route to the last eight, will face either fellow Welshman Mark Williams or last year’s surprise semi-finalist Si Jiahui in round two.