Leinster's Cian Healy and Jack McGrath are out on their own for Ireland.
At least, this is the perception from the outside as Healy and McGrath work in tandem for club and country.
There has been something of a one-on-one battle at Munster too where Dave Kilcoyne and James Cronin have been vying for supremacy at loose head prop.
Kilcoyne has taken up the challenge to provide a physical impact that has not gone unnoticed.
"I was very happy coming here with my form for Munster," he said of Ireland camp in Carton House.
"You're just trying to get as much game-time as you can in this environment to push on.
"I'm just trying to put my best foot forward with every chance I get."
The last time Kilcoyne was seen in green was in that impressive cameo against Italy at Soldier Field earlier this month.
For all the personal disappointment around not making the cut for New Zealand, Kilcoyne was left in no doubt about why he had not and how he could, in the future, change that.
Joe Schmidt is the main man in a team of coaches that examine the finer details of all the players' minutes.
"There's definitely more I can be doing," Kilcoyne admitted.
"We got incredible feedback when we came into camp.
"If you saw the detail of how all our club games were analysed in terms of attack and defence.
"Simon (Easterby) has all our stuff within our forwards and Faz (Andy Farrell) would have all our individual defence clipped and he'd know exactly how many impact tackles, how many carries you made. (Greg) Feeky would have all your scrum work and where you can improve broken down and ready to go for you."
The 29-year-old wants to leave everything on the pitch against the USA on Saturday, for however long he is out there.
The standard has been set by Healy and Tadhg Furlong, both visibly exhausted when replaced.
"I thought it was the best game I've seen Cian play in a long time," admitted Kilcoyne.
"I thought Tadhg had a great game, they both emptied the tank and what more can you ask for, and then bring on the lads to bring fresh legs.
"When I go out, I literally go out to empty myself as best I can - and then bring on the cavalry."
Meanwhile, Juliet Short will make her Ireland debut at NO.8 against England in the Women's international at Twickenham on Saturday (Live Sky Sports Action, KO 5.40).
Coach Adam Griggs makes a total of six changes, including St Mary's College hooker Emma Hooban starting for the first time, for a second cap.
Old Belvedere's Ellen Murphy should make her international debut off the bench.
Ireland (v England): L Delany; E Considine, S Naoupu (capt), M Claffey, L Sheehan; N Caughey, N Cronin; L Peat, E Hooban, L Lyons, A McDermott, N Fryday, J Deacon, C Molloy, J Short.
Replacements: S Mimnagh, L Feely, F Reidy, C McLaughlin, E McMahon; A Hughes, E Murphy, B Parsons.