Mo'unga knows first-hand how dangerous Russell can be, having been on the receiving end of his class when his Linwood side experienced a masterclass turned on by Russell in the wet for Lincoln University in Christchurch club rugby.
Russell was on a 15-week scholarship in Christchurch and played for various clubs during his stint.
Lincoln University was nicknamed Canterbury B because of the quality of their players, while Mo'unga said he played for Linwood, who had just enough to field a team.
Russell exhibited his potential every time he played in Christchurch, including playing for assistant coach Jason Ryan's Sydenham club.
Mo'unga said, "We knew when he arrived that the sky was the limit for him in terms of what he could do back then, and to see him grow as a player, and the confidence he has, and the flair he has separates him from any other 10."
Going up against Russell was something Mo'unga was looking forward to because he enjoyed watching him and rated him one of the best five-eighths in the world.
"He can play all types of games - his kicking, his running, his passing. We go a way back. To see him since then become the player he is now is awesome, and, a top bloke as well.
With an extra day to prepare for a Sunday game locally, their post-game review was delayed until Tuesday, and while they were happy with their performance against Wales, there were still aspects for improvement.
"We know the challenge ahead and how tough this team is, and how important it is to reset and look at the new opportunities ahead, but also the challenges of what we're going to do during the week, so we're best prepared for them."
Ryan said the challenge for the side this week was how to be better?
There had been some satisfying lessons and growth from the Wales game, but there were areas they needed to be better against Scotland.
"We know Scotland will bring a different challenge, they're a very good defensive team and awesome around the contact so it'll be another step up and we'll step up with that."
Ryan said the emphasis with the side was never being satisfied and challenging them to keep building in performances and habits.
"That's one thing we have really challenged in the last three months just not being satisfied where we are at and understanding that international rugby and where it is at the moment teams are getting better so that's a focus for us."