The talented 20-year-old was a relative unknown outside of snooker circles when he arrived in Sheffield, but is suddenly the name on everyone's lips after edging a step closer to becoming the youngest ever winner of the World Snooker Championship.
The fresh-faced 20-year-old, a 200/1 outsider when he set foot in the Crucible in April, has enjoyed a dream ride past Shaun Murphy, Robert Milkins and Anthony McGill to become the youngest World Championship semi-finalist since Ronnie O'Sullivan back in 1996.
Now a shot to go the distance, Si is also the first debutant to reach the last four since Andy Hicks in 1995, leaving him just two matches away from becoming the youngest ever world champion and the first rookie to lift the famous trophy since Terry Griffiths in 1979.
Chinese snooker has long threatened to produce a world champion.
Ding Junhui was seen as the anointed one, arriving at the Crucible in 2007 for the first time with a UK Championship title already under his belt.
A year later Liang Wenbo went on a thrilling run to the quarter-finals with a swashbuckling style which marked him down as another to watch.
Neither player has gone on to lift the trophy - Ding came close in 2016 when he reached the final - while many more Chinese aspirants have followed them on the trail to the Crucible but ultimately fallen short.
So now it's Si's turn to shine, to delight fans with his cavalier, carefree game, and maybe jump to the top of the queue of Chinese contenders ready to make that ultimate leap, to become that nation's first-ever world champion - a feat he is now 17/2 to pull off.
While he's far from a veteran of the sport, Si has undertaken a grounding on the professional tour.
He first got a tour card in May 2019, two months shy of his 17th birthday, and within a few months had claimed the scalps of players of the calibre of Stuart Bingham and Hossein Vafaei.
However, his two years on tour were largely unsuccessful but, undeterred, came back as an amateur, famously incurring the wrath of Shaun Murphy at the UK Championship in November 2021, beating the former world champion 6-5, who vented his fury that amateurs were even allowed on the same table as the pros.
Three months later Si returned to the ranks of the professionals by thumping Lee Stephens 5-0 to win the WSF Open and regain his card.
Si's first year back on tour has hardly been a roaring success and he was ranked a lowly 74 when he turned up at the English Institute of Sport in Sheffield for the qualifiers.
He survived a fightback from Austria's Florian Nussle in his first match - he built up a 9-1 lead but limped through 10-7 - to set up a showdown with established English star Tom Ford.
Ford was up to No.23 in the world coming to the end of an excellent season in which he had reached the UK Championship semi-finals and, as recently as February, the final of the German Masters.
A tough, calculated opponent, Ford would represent a challenge to anyone - and Si beat him 10-5.
Message sent, he then toppled another higher-ranked opponent - Northern Ireland's Jordan Brown by a 10-7 scoreline - to make it to the Crucible for the first time.
Now people were beginning to know a little bit more about this starlet from the Far East, and pretty soon his career would have lift-off.
All eyes were on the big guns at the start of the tournament with Ronnie O'Sullivan's quest for a record eighth crown the major talking point.
The Rocket lights up the Crucible, he has done for years. But not for much longer and now he's not the only one. Step forward Si Jiahui.
As luck would have it - for mischief-makers anyway - Si was paired in round one with Murphy, the fourth seed whose stinging words of criticism from their meeting at the UK Championship two years ago were doubtless echoing around his young opponent's head, giving him both inspiration and motivation.
There haven't been too many last-frame deciders at this year's World Championship but Si has been involved in two, the first against Murphy.
And the fact that he's still standing tells you he's got the temperament to go with the talent.
Si, by now ranked 80 and the lowest-ranked player in the final stages, immediately showed he was nerveless by coming from 3-1 down to win the first session 5-4.
He increased that lead to 9-6 before Murphy's gutsy comeback but any sense that Si would be over-awed and simply wilt were utterly unfounded.
It was Si not Murphy who held himself together, took the decider leaving the 2005 champion to proclaim: "I threw everything at him. I tried my absolute best and still lost. He will be China's first world champion."
Si had put himself on the snooker map, the sporting map. One can only imagine the excitement back home in China after watching one of their own, this precociously talented star, see off one of the game's legends.
To win once of course is great, but following it up is more of a challenge, a challenge Si has proved more than capable of meeting with subsequent successes over Robert Milkins and Anthony McGill, the latter in another final-frame showdown.
So here he is, in the semis, up against ninth seed Luca Brecel, the man who derailed the Rocket and now an 11/4 chance to win it all on Monday evening in Sheffield.
It looks like the Chinese snooker baton has been handed over, from Ding, via Liang and several others, into the trusted grip of Si Jiahui, prodigiously gifted, completely fearless and who knows, maybe about to be crowned the youngest ever world snooker champion.
With four-time champ Mark Selby (11/10 To Win Outright) and player of the season so far Mark Allen (10/3) on the other side of the draw, there's much ground still to cover but this talented youngster has been taking everything in his stride so far and it's dangerous to dismiss him as the outsider of four still standing inside the Crucible cauldron.