The 20-year-old's spell on the field was brief - just seven minutes - as regular No.9 Mike Phillips moved to centre to replace crocked Andrew Bishop.
The debut represented a meteoric rise for the Scarlets youngster, who this time last year hadn't started a game of regional rugby and was well down the pecking order in this season's RBS 6 Nations campaign.
"It went quite quick, but it's just a great experience and you want more of it," said Knoyle.
"It was a bit weird sitting on the bench. I was thinking of the game and trying to concentrate really.
"I was looking at what Mike was doing and watching where he was standing, to make sure I got in the right position.
"It was just a check-list really, making sure I knew the calls, going through them in my head.
"The atmosphere was great and I wanted to come on and do my best."