While Williams has experience of playing Sevens (he figured prominently in last season's campaign before injury curtailed his progress), Knoyle is a complete novice but John has no qualms about throwing the Gloucester-bound scrum half into the deep end, along with his Scarlets teammate Adam Warren who will also be enjoying his first taste of Sevens rugby this weekend where Wales face France, USA and Russia in Pool D.
"They [Knoyle and Warren] may be considered 'surprises' as they are new , but they have trained well within the environment and it's exciting to have them in the squad. Hopefully they will enjoy the experience and bring something new to the squad," explained John who has guided Wales to their current overall position of seventh in the series standings.
"Both are good rugby players, both work hard in games, and they have got a good work ethic. We're looking forward to see them perform on the sevens circuit," he added.
Gareth Davies and Tom Grabham will make their first appearance of this campaign but along with Williams, they possess previous experience with Wales at this level.
"We're grateful to the regions for allowing us to use the players and with this weekend's tournament and next week's event in Twickenham considered 'home' tournaments, we've taken advantage of players becoming available.
"We've also brought in Chris Knight from Llandovery. He has been a standout player in the Premiership. Llandovery play a cracking style of rugby and he's been scoring a lot of tries. He's excelled in training and deserves his chance."
While some may view Wales' group as one of the weaker pools, John doesn't see it that way.
"It's a difficult group. We've got France who are just two places above us, USA who are fighting for survival and Russia who have a massive tournament the week after. It may look promising on paper but we know it's going to be very difficult. All teams in our group have lots to play for. Hopefully we can get out of the group but it's going to take a massive effort."
Wales Sevens squad for Emirates Airline Glasgow Sevens, May 4-5:
Craig Price, Adam Thomas. Rhys Shellard, Tavis Knoyle, James Davies, Lee Williams, Alex Walker, Gareth Davies, Adam Warren, Tom Grabham, Owen Williams, Chris Knight