He has been a dynamic ball-carrying threat all Rugby World Cup but today Ma'a Nonu must take on guidance and leadership responsibilities as well to steer Colin Slade through the minefield of knockout rugby.
Nonu tends to be more a man of action than words; he usually lets Dan Carter and Conrad Smith do the talking, the strategic planning and organisation required out on the field. But tonight, with no Carter, the obligation lies with Nonu to try to help Slade stay composed.
Nonu is probably the All Black player of the tournament so far. He's been consistently outstanding - available to smash over the gain line and play the next man into space.
No one ever talks about the Nonu of old - the one who could break the line but who was prone to fuzzy thinking and erratic execution.
The new Nonu is mature and exact. His mistakes are infrequent; his power is constant - the one single commodity that everyone can recognise and admire without having it pointed out.
The tournament shifts into a new phase tonight with double connotations for the All Blacks. First, they have to deal with the intensity and tension that will come with this game being a knockout test; they have to adjust to playing without Carter.
It's one thing to not have him against Canada; a totally different proposition to take on Argentina without their engine, their tactical maestro and chief organiser.
Slade will be starting just his fifth test. He's a tidy and organised player, clearly resilient given his efforts to overcome two jaw breaks earlier this year and armed with self-belief and natural confidence.
He's a prospect; a keeper, for sure, but as Graham Henry pointed out last week, Slade lacks time in the saddle. "He just needs more football, so the more times we can get him out there, the better he's going to be."
Life will be that bit easier for Slade if Nonu can maintain a steady and helpful chatter. Nonu can do more than is realised in helping Slade see the space, make the right calls and come up with the right plays.
First five can be a lonely, exposed place for an inexperienced youngster making his way. Aaron Cruden found that out last year when he had to start in Carter's absence. It was the final Tri Nations game in Sydney - the tournament already safe but the pressure on to keep a winning run going and to further attack the fading belief of the Wallabies.
Cruden's confidence was shot after 20 minutes. He picked up a nasty knock on his ankle in his first contact and struggled from there. All aspects of his kicking were poor and the swagger that had taken him through Super Rugby was nowhere to be seen.
Test rugby suddenly looked a step too far for Cruden. He wasn't helped by the fact the All Black forwards were sluggish and off the pace for the first 60 minutes; nor by the fatigue Conrad Smith was clearly feeling on the night. Normally Smith would have been vocal and authoritative but he was struggling to stay in the game.
Nonu provided his usual direct threat that night but he and Cruden may have been at cross purposes in terms of how they saw the game. Nonu has to be positive in his commentary and prepared to forgive Slade the mistakes that have been a feature of his games so far.
Sonny Bill Williams put it well when he was asked what it would mean for the backline not having Carter: "I think we all, not just the starting 15 but everyone involved, not just the players, the coaching staff as well, we just need to raise the bar a couple of per cent each. What's done is done and we can't turn back time, we've just got to concentrate on the positives and that's what we're doing as a squad. We probably won't change too much in the backs, but just try and raise our game a couple of per cent each.
"Hopefully we can still express ourselves out there and still play with the freedom we have been playing. But also we've got to acknowledge that this is knockout rugby, that there's no tomorrow. You've just got to find the right balance, not go into your shell, still express yourself but obviously know that it's finals time."
Nonu was an important part of the All Black package in the pool round. He is going to be critically important in the knockout rounds.