Mark Allen leads World Championship debutant Mitchell Mann 6-3 after the opening session of their first round match at the Crucible Theatre.
The world number seven trailed 2-1 but reeled off the next five frames, before Mann secured the last to trail by three going into Wednesday’s second session.
Antrim man Allen, 30, was a semi-finalist in 2009 but has not been beyond the second round since 2011.
The winner will face Joe Perry or Kyren Wilson in the last 16 in Sheffield.
Mann is the only rookie in this year’s tournament and beat the Northern Irishman in qualifying for the China Open earlier this season.
The Birmingham player, 24, booked his place at the Crucible by beating Thai talent Dechawat Poomjaeng 10-9 in the final qualifying round last week and at world number 74 is the lowest ranked player in this year’s first round draw.
Allen, who wonw the Players Championship last month, his third success in a ranking event, reached the world quarter-finals in 2010 and 2011, but has been defeated in the second round in both of the last two years.
A break of 69 helped Mann win the opening frame, but Allen replied with 74 in the second to level the match.
A clearance of 77 nudged the English player in front again but when he missed a straightforward black in the fourth, Allen cleared up with a break of 64 to restore parity at the mid-session interval.
Breaks of 104 and 85 helped Allen into a 4-2 lead and he went on to win a scrappy seventh frame to further extend his advantage.
Mann got off to a good start in frame eight, compiling a 34 break, but his opponent responded with a 78 clearance for 5-2.
A cagey final frame finally went the way of Mann as he reduced his deficit ahead of Wednesday morning’s resumption.