Si fell off the main tour at the end of last season and only entered the UK Championship as an amateur top-up in the field.
Having dominated from the outset and led 5-1, the Chinese rookie looked to have let his chance slip when watching Murphy rally to 5-5 and then appear on course to win the deciding frame.
However, when the 2008 champion missed the final blue, Si stepped in to claim a famous victory, one which left Murphy furious.
Murphy told BBC Radio 5 Live afterwards: "I feel extremely hard done by that I have lost to someone who shouldn't even be in the building.
"I don't know why we as a sport allow amateurs to compete in professional tournaments. This is our livelihood. This is our living. We are self-employed individuals and not contracted sportsmen. We don't play for a team.
"The other 127 runners and riders in the tournament, it is their livelihood too. It is wrong, in my opinion, to walk into somebody who is not playing with the same pressures and concerns I am.
"He played like a man who does not have a care in the world, because he does not have a care in the world. It is not fair, it is not right.
"I am not picking on him as a young man, he deserved his victory. Amateurs should not be allowed in professional tournaments, the end.
"This is our livelihood. This is how I put food on the table. This is how I earn money. Since turning professional at 15, I have earned the right to call myself a professional snooker player. He hasn't done that. He shouldn't be on the table."
