Jack Lisowski secured a 6-3 lead against Matthew Stevens in the second qualifying round of the World Championship.
Stevens opened up with a first-frame century clearance of 135, which was followed up with a century clearance from Lisowski to level things.
The third frame was far more hard-fought as it went down to a 51-49 decider on the final black, with an excellent cut from Lisowski to go 2-1 ahead.
In the final frame before the mid-session interval, Stevens resorted to the extension when 31-0 up for a red into the bottom right pocket, and his scoring ended on 39 when the red appeared to roll off something on, or under, the surface of the baize.
Stevens returned back and built a 65-36 lead, but had the ball tucked up behind the brown as he looked for the yellow down the bottom of the table. He missed on his first attempt, and gave Lisowski a chance to double his lead if he could make a tricky, long pot.
The Englishman sunk the ball and he measured the shot expertly to land on the green. He moved onto the blue, needing to reach the pink, right at the top of the table. While he manoeuvred the ball adroitly he gave himself a tight angle on the black when he was five points behind.
Lisowski missed to give Stevens a black, needing to avoid the in-off with the white, and he tied up the frame to go in level after four frames.
Lisowski went back in front with a fluid break in the opener after they came back to the table, but Stevens showed his form was intact to make it 3-3 with a 97.
Stevens fell behind once more as his opponent switched between left and right hands after blasting into the pack, taking the reds off the cushions to reach a break of 80 to regain the advantage.
A coughing fit from Stevens led to him leaving the table for a few moments before coming back to try and reel in a 47-0 deficit. A stroke of bad luck let Lisowski back in, and he faced a tough red to go 60-6 up, but he missed and left Stevens with a long red or snookers as his options, but he could not prevent another frame loss.
The Welshman looked to be a little under the weather after his coughing problems but he gave himself a shot at ending the session just a frame behind when he set himself up for a blue with an 11-0 lead, and he laboured to make that 30-0 before setting Lisowski up with a tricky shot selection from well up the table.
The previously high standards of the match so far fell away after a string of poor shots from both players was put out of its misery when another slack miss from Stevens allow a misfiring Lisowski to bring the session to a close with a 6-3 lead ahead of the evening resumption.
Elsewhere in the qualifiers, Dominic Dale holds a 5-4 lead over He Guoqiang, Louis Heathcote is 5-4 up against Stuart Bingham, and Lyu Hoatian trails Jenson Kendrick 5-4.
There are four matches yet to finish their first session: Ricky Walden v Mark Davis, Zhou Yuelong v Jak Jones, and Stephen Maguire against Yuan Sijun.