As the All Blacks relax during their week off from the Rugby Championship, coach Steve Hansen could be forgiven for feeling a little anxiety as he waits for progress reports on Luke Romano's shoulder injury.
The Crusaders lock has played only two tests for the All Blacks but already has become an extremely important cog in Hansen's machine, and apart from Conrad Smith and Tony Woodcock, is the only one with a question mark over him in terms of fitness.
Hansen has recently referred to his liking for combining a big, physical, player alongside a "skinny" one in the second row.
With the wiry Sam Whitelock, still only 23, and a relative veteran of 29 tests, virtually an automatic selection for the All Blacks, that puts a big onus on the 26-year-old Romano. The other option, Brodie Retallick, 21, is in the Whitelock mould but has also performed spectacularly during his breakthrough season and will start in the All Blacks' next game, against the Pumas in Wellington a week on Saturday, if Romano doesn't.
Below these three, however, and the cupboard is a little bare - the massive hole left by Brad Thorn's departure not quite filled yet. Craig Clarke, the impressive Chiefs' captain, has been included in the All Blacks' recent Auckland training camps, officially because the medical staff are monitoring his knee injury. Nevertheless, he wouldn't be getting such care if he wasn't on Hansen's radar and Clarke appears to have overtaken Jarrad Hoeata of the Highlanders as the next best.
Ali Williams is an incumbent, but also has a knee injury which he aggravated in the second test against Ireland in June. Already struggling for form with the Blues this season, his best hope of a playing return following surgery is for Auckland in the second half of the ITM Cup. Whether the 31-year-old makes the end-of-year tour remains to be seen, although Hansen is a big supporter, mainly due to the experience the player's 75 tests provide.
Romano, who on Saturday against the Wallabies received a knock to a shoulder which troubled him for the Crusaders this season, offers a ball-running and defensive edge that neither Whitelock nor Retallick can quite match and Hansen will be eager to retain his services for the match against the physical Argentines.
And Hansen won't be the only one. With only three locks named in the squad, Hansen has raised the prospect of Kieran Read being press-ganged into the second row, something which the free-running No8 won't be overjoyed about.
The match in Wellington will be a significant one for centre Smith, if he does recover from his detached retina as Hansen believes he will. His quiet organising will be important in order to get the best out of Ma'a Nonu, returning to second-five following Sonny Bill Williams' exit. Nonu hasn't looked his best in his first two tests of the year, but is likely to be more comfortable at second-five alongside a player who so clearly complements him, rather than Williams, who is a similar type of player.
Loosehead prop Woodcock is on track to return from a rib cartilage injury, according to Hansen, who will be hoping for similar news on Romano.
With obvious depth in every other position - the All Blacks now have an embarrassment of riches at halfback and first-five following a few lean years - lock is the one position of comparative vulnerability, although how Robbie Deans would love to have such trifling concerns.