Three-time champion Mark Williams admitted he does not know whether he has played his last World Snooker Championship match after he suffered a dramatic 10-9 defeat to Si Jiahui in the first round.
Si continued his love affair with the Crucible as he followed up last year's surprise run to the semi-finals by knocking out Williams in an epic clash.
Williams resumed with a 5-4 lead but it was the Chinese 21-year-old who hit the ground running on Tuesday, taking each of the opening four frames to go into the mid-session interval 8-5 in front.
Williams then won four of the next five to make it 9-9 and set up a decider, with Si holding his nerve to close out a narrow victory.
While Si will face Jak Jones in the second round, Williams confessed he did not know whether a return to the Crucible is on the cards but appeared to rule out immediate retirement.
When asked whether he will be back next year, Williams said: "Who knows? I'll be 50 years of age next year.
"I looked around and loved every minute of it. Whether or not I'll be back again, I don't know.
"I'm not considering my future really, just it's a tough game. You keep getting back to these venues and it's hard.
"Most of the ones for a while now, you've just got to treat it as if you're not going to get back here.
"I'm not retiring, just treating every one as your last one. Fingers crossed you'll see me playing next year, who knows?"
Si made a lightning-quick start to the session, striking the ball with increasing authority as he reeled off four frames in a row with three breaks in the 60s.
Williams' fightback began immediately after the mid-session interval as he reduced his arrears to 8-7.
Si bounced back to take the next frame with a nerveless display before Williams battled to victory in the next two to level the match and force a decider.
But Si reeled off a break of 77 to wrap up a memorable win.
He said: "The first half of the match was quite nip and tuck, neither of us had brilliant form.
"But later on he gave me a lot more chances to let me have that lead at 8-5. My opponent was really, really accurate towards the end so it went all the way to the deciding frame.
"I always thought 'I am the challenger who's trying to take him down', so I didn't really feel the pressure and that's how I won it."
World number three Mark Allen built up a commanding 7-2 lead in his encounter with Robbie Williams.
Allen won the first three frames before Englishman Williams hit back with a break of 86.
Allen won a mammoth fifth frame before stretching his advantage to 6-1. After his opponent won the next with a century, Allen made it 7-2 to leave himself three frames from victory.
Jack Lisowski forged a 5-4 lead in his World Snooker Championship opener against Ding Junhui as the clash lived up to its billing as the tie of the round.
Lisowski, who reached the quarter-finals at the Crucible in 2022, had to qualify for this year's tournament after dropping out of the top 16, beating Matthew Stevens 10-3 last week to book his ticket.
But after falling behind early on against Ding, Lisowski looked back to his best as he edged a highly entertaining first session.
Lisowski, 32, looked in danger of being blown away by Ding on Tuesday morning as the 2016 finalist flew out of the blocks, compiling a clearance worth 127 to win the opening frame.
The Chinese star then enjoyed a huge slice of luck in the second as he fluked a red into a middle pocket early on, but a missed black at 23-0 opened the door for Lisowski to pot his first ball of the day.
Lisowski was only able to score a solitary point at that visit before letting Ding back in, though, and he finished the frame with a break of 60 to make it 2-0.
The Englishman hit back in the next, rattling off a break of 72 to reduce Ding's lead to one.
And Lisowski went into the mid-session interval tied at 2-2 courtesy of a break of 91 in the fourth frame.
Ding displayed his brilliant battling qualities in the fifth frame as he conjured a 98 to edge ahead once more.
An attritional sixth frame, which lasted more than half an hour as a tactical battle broke out, went Lisowski's way as he drew level.
But Ding made quick work of the next frame, winning it with a break of 90 to go 4-3 up before Lisowski took the eighth.
And Lisowski won the final frame of the session to lead for the first time in the match.
Former finalist Kyren Wilson has one foot in the second round after storming into an 8-1 lead against Welshman Dominic Dale, who is making his Crucible comeback after a 10-year absence.
Wilson started brightly, winning the first two frames before Dale seemed set to get his first frame on the board after opening up a 30-0 lead in the third.
But Wilson made Dale pay for missing the pink as he roared back with a break of 75 to take a 3-0 lead.
Dale was not to be denied in the fourth frame, though, producing a stunning break of 120 to get on the scoreboard.
Wilson regained command immediately after the interval with a phenomenal break of 123 before a 98 in the next frame moved him 5-1 in front.
Englishman Wilson then showed exceptional nerve to come from behind to win the next frame 74-70 to extend his lead to five.
Wilson's dominance continued as he won the next two frames with breaks of 77 and 73 to extend his massive lead.
Robert Milkins, the 16th seed, held his nerve in a tense final-frame decider to edge China's Pang Junxu 10-9.
Milkins trailed 5-4 overnight and won the first two frames before an attritional see-saw battle ensued, with neither player making a century break in the match.
World number 27 Pang led 9-8, but Milkins hit back to level with a run of 76 before edging the decider.
World number 15 Barry Hawkins will resume on Wednesday evening 5-4 down against Welsh qualifier Ryan Day.
