But since his man-of-the-match display against Scotland last March, Ryan had looked right at home in the Irish second row whilst making seven successive Test starts.
In the absence of the talismanic Paul O'Connell, the Tipperary man bossed an engine room that has led by example during this month's GUINNESS Series.
Mike McCarthy was man-of-the-match in the 16-12 defeat to South Africa and his second row partner Ryan took the honours for an accomplished 80 minutes against the well-beaten Argentinians.
Speaking straight after Saturday's 46-24 success at the Aviva Stadium, he highlighted how the players delivered under pressure given the need to win and secure Ireland's second tier seeding for Monday week's Rugby World Cup draw.
"We really wanted to put in a good performance for the supporters and we're delighted they really got behind us today," said Ryan.
"We were really under pressure this week (with the rankings scenario), but doing some great things in training that needed to come out on the field for 80 minutes.
"We're delighted to be in the top eight (for the Rugby World Cup draw). Hopefully we can carry this (winning) form into the Six Nations and take it from there."
Ryan was at his combative best in the loose and produced a dominant performance in the lineout, combining superbly out of touch with try-scoring hooker Richardt Strauss.
The soon-to-be 29-year-old won six of Ireland's own lineout throws and gained an early steal, while making nine tackles and six carries overall.
Ryan deflected the plaudits onto his pack colleagues, adding: "From the guys who came in off the bench to all the forwards, they put in a massive effort.
"Cian Healy, Straussy did brilliant, Mike Ross did brilliant, Mike McCarthy another outstanding game, Peter O'Mahony, Chris Henry, Jamie (Heaslip) - they all did fantastic."
Hard graft was certainly the order of the day for the Irish forwards, who held the edge in the set piece and rucked and tackled aggressively throughout.
Flanker Peter O'Mahony was in the thick of the action at the breakdown. He also reached double figures in terms of his runs in possession (10) and secured three lineouts for the men in green.
Picking out some of his team-mates for their work in analysing the Pumas, the Corkman said: "We learned lessons from South Africa and the Fiji result gave us a great boost, it was a huge boost for the squad.
"I can't give enough praise to fellas like Donnacha for the amount of home work he does in lineouts and stuff and Mike Ross for the detail in the scrummaging, Cian Healy and Straussy for the endless time they spent on the laptops looking at fellas.
"We talked all week about doing ourselves justice. We owed ourselves a performance. We wanted to play well and we sat in the dressing room afterwards and there was a good feeling that we did that."
The 23-year-old now has nine Ireland caps to his name, having earned his stripes during this year's RBS 6 Nations and the summer tour to New Zealand.
O'Mahony, who filled the blindside role against the 'Boks and Argentina, is hugely determined to hold onto a starting jersey come February and the Six Nations.
With regulars Sean O'Brien and Stephen Ferris coming back off the injury list, the scrap for back row places will intensify in the coming weeks. But O'Mahony is undeterred and insists that the younger players have to stand up and be counted.
"We're going to have players coming back from injury so there will be great competition for the Six Nations and after this performance fellas will be hopping to get back into Irish mode and get stuck into the Championship, but obviously we have other things to worry about now.
"We go back to our provinces now and worry about our back-to-back games in the Heineken Cup, but from an Irish point of view we'll be looking at the Six Nations and just play over the next few weeks to stick your hand up for that squad.
"There is a young squad here. Hopefully we'll be taking this team to the World Cup and stuff. Hopefully we will have laid down our own markers.
"We have to take control of this team. It's going to be our team for the next few years. We just have to play well and stick our hands up for selection," he added.