If Ryan with 21 caps is the veteran of the group then Kilcoyne, on the cusp of his first ca,can be considered the cub. And his rise has been meteoric.
At the start of this season he had four senior caps to his credit - one start and three off the bench - but injury to Wian du Preez provided the former Ard Scoil Ris student with the launchpad and he has grabbed his opportunity with both hands.
So today the 23 year old finds himself sharing a room with Ryan in the Shelbourne Hotel and admits that he's 'really enjoying the whole experience.'
"Carton (House) is brilliant. Get up, less than five minute walk to training, everything right there beside ye.
"Looking back," he continues, "I think the competition for a place in the Munster team with Marcus Horan and Wian has brought out the best in me and helped me get here. Their help has been great. That and Paul Mac (McCarthy). He's been a huge influence. I've had him since my Academy days, right through the As and then when I came into the senior squad. He's been a huge help. Always available if I need advice."
He also cites the input of former Elite Player Development Officer Ray Egan and Fergal O'Callaghan (S&C coach) while he was in the Munster Academy player and now Bryce Cavanagh, Munster's Head of Fitness who he credits for having him in the condition he's in, "We did a lot of work with Bryce over the summer and I think my conditioning levels are very good."
On his last visit to the Aviva, Kilcoyne was up against his now Ireland team-mate Mike Ross, and though, Ross mighn't admit it, Kilcoyne gave him a torrid time. " Yeh I thought I did ok. There was an issue there with the bind before half time which was maybe fair enough, I dunno. But overall I was happy enough"
Tomorrow he may get another opportunity to display his wares on the biggest stage.
Ireland (v South Africa): S Zebo, T Bowe, K Earls, G D'Arcy, A Trimble, J Sexton, C Murray, C Healy, R Strauss, M Ross, D Ryan, D O'Callaghan, P O'Mahony, C Henry, J Heaslip (capt). Replacements: S Cronin, D Kilcoyne, M Bent, D O'Callaghan, I Henderson, E Reddan, R O'Gara, F McFadden.