Knoyle was part of Wales' World Cup squad but his game time was limited to a solitary match against Namibia as he had to play second fiddle behind Mike Phillips and Lloyd Williams in the pecking order.
And if the 21-year-old didn't already have enough incentive to lay down a marker, he is coming head-to-head with the region that released him as a youngster.
"I'm just happy to be back and getting stuck in with the region again," he said.
"The World Cup was good. On a personal note it wasn't what I wanted to get out of it, but, from a team perspective, it was brilliant. It was frustrating, but it was a case of supporting the boys all the way.
"It is a case now of coming back here and knuckling down again.
"There is always that extra spice to this fixture, but you have got to enjoy it," he added. "As a kid I used to go and watch these games on a Boxing Day.
"There is a great tradition with these fixtures and it is great to be part of it.
"It is a huge game for us. We have done well in the last few games, it is a case of trying to go to the Liberty [Stadium] and upsetting the Ospreys.
"Most of the boys are back now and it was great to see how a lot of them went in New Zealand.
"It is tribute to what has been happening at the Scarlets in the last few years."
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