Players talk about Johnny Sexton and how he's like a coach on the pitch but outside of calling moves what does that really mean? Leinster were leading 19-9 going into the final ten minutes of the PRO14 semi-final against Munster at the RDS last May.
Sexton had come on over 10 minutes earlier and was typically buzzing around like a man working to a different deadline than everyone else. Any Munster player who'd already an hour of this game in their legs must have wondered what kind of fresh hell was this coming up against a just-off-the-bench Sexton who was pulling moves like fooling a tiring Tadhg Beirne with a dummy-pass.
What about his own team-mates? After 72 minutes, a few of the Leinster players were slowly getting to their feet when Sexton ran over and shouted at them: "Get up! Get up!" Who needs a coach pointing out areas to improve at a Monday video review session when Sexton is doing it in real time during a game.
Like Paul O'Connell once noted, Sexton not only knows his own role inside out, he also knows everyone else's.
The only surprise about Sexton being named Ireland captain on Wednesday was that there was any surprise at all. Has there ever been a player in the professional era as vocal, as influential, as pivotal in an Irish team and not been the captain the way Sexton had been with Ireland?
For those with concerns that Sexton might still be captain for the 2051 World Cup, relax, we don't know how long he'll be captain for. This era of Sexton as Ireland captain won't just be defined by results but also by relationships - his relationship with his team-mates, his relationship with Andy Farrell and his relationship with referees.
Besides taking over mid-game, only once before has Sexton started an Ireland game as captain. So why does it feel like Sexton needs to change for a role he's rarely done?
Rewind for a sec to last year's Six Nations. In the build-up to Jacob Stockdale's try in the first half of the Scotland game in Murrayfield, you'll remember how Sexton delayed his pass to Stockdale to the final millisecond which meant the Scotland prop Allan Dell had fixed himself so hard on devouring Sexton that he left space for Stockdale to zip through and score.
It was an impressive but harmful selfless act by Sexton who got the full force of Dell. Two weeks later, Sexton was getting it in the neck by some commentators for his demeanour against Italy in Rome - for giving out to Stockdale for over-running a pass and for kicking a water-bottle in frustration as he came off. The drive and passion that is loved about Sexton can become the very thing that's viewed as a liability when things go badly.
If Brian O'Driscoll's dressing-down of Peter Stringer for throwing an intercept pass in the 2007 Rugby World Cup against Georgia had happened in the last World Cup, it would have been inflated to a national incident.
But there were fewer TV cameras back then, less social media, whereas now everything is picked up, every argument and every kicked water bottle. Maybe we're also more aware of how different sport can be to everyday work-place conduct.
Two years ago Luke Fitzgerald described how he was "rinsed" by Joe Schmidt at a training session during the 2015 Rugby World Cup.
"The player's recall of the lead-up to the 'rinsing' wasn't accurate, but I still needed to be conscious of how I delivered the feedback," Schmidt wrote in his autobiography. "I often explain to players before we train that I am going to try and exert as much pressure as possible on them during training to best prepare them for the stresses of the Test-match arena".
We never saw what Schmidt was like during those sessions but if we're to take that view that Sexton's role is like a coach on the pitch, then calling out players and showing frustration in public is a style of leadership that can leave itself open to public criticism. Iain Henderson said after that Italy game that players shouldn't take it personally when Sexton shouts at them.
"As a younger player in the squad, I got shouted at by Johnny loads of times. It used to get to me a wee bit but I remember it being explained to me that he's doing it because he cares so much," Henderson said.
Sexton is feisty, no doubt, but his personality might also come across as more dominant because the personality of the players around him (I'm using a broad brush stroke here, admittedly) is perhaps less extrovert than the personality of players he played with in the past.
Leinster senior coach Stuart Lancaster spoke this week about how he believes young Irish players are more introverted than English players.
"If I talk about the Irish system I think that the schools system is very teacher-led, very coach-led," Lancaster said in an interview with the BBC's Rugby Union Weekly pod. "They're very used to being given the information and can deal with detail. I wouldn't say it's a strength all the time 'cos sometimes I'm trying to coax them out of that personality to a more extrovert personality - where they're happy to talk in a meeting, where they're happy to take the lead in a session. It's just getting the balance."
Sexton was described in the past as Schmidt's voice on the pitch. If this new national regime wants to be seen as less controlling and less regimental, how does that extend to how Sexton plays under Andy Farrell? Perhaps never before has the relationship between a new Ireland head coach and his captain been as important.
This is Farrell's first head coach gig so it's not a huge leap to suggest he'll lean even more on the experience of Sexton. A starting point will be to learn from the last World Cup and the anxiety that hung over the squad.
It's clear there was some communication breakdown between the leadership group, in which Sexton was a vice-captain, and Schmidt, who Farrell was assistant coach to, after Rory Best's claims last month that there was "too much detail" from the coaches which created "too much tension".
The sale of ref-links might also get a spike in this Six Nations. Sexton's "I know you hate me, but you have to talk to me" chat-up line to referee Pascal Gauzere during Ireland's tour of Australia two years ago is unlikely to get another airing. There were signs of improvement in Sexton's communication style and body language with referees as Leinster captain before he got injured earlier this season.
Sexton plays on the edge so it's understandable his terms of engagement would need a bit of bedding-in time to balance with a temperance his new role requires when dealing with refs. The campaign for James Ryan to be made Ireland captain was understandable.
But just because O'Driscoll was made captain at 23 doesn't mean it was right for Ryan to be made captain at 23 when the responsibilities a captain has, like dealing with the ref and spotting incidents for the TMO to review (as well as what Lancaster said about young players, generally, above) have changed hugely. Farrell should make Ryan vice-captain and see how that responsibility rests with him for a few years and then make a call before the 2023 World Cup.
He's 34 yet the contradiction is this feels like a coming-of-age period for Sexton as a captain. A leadership guru will tell you that a true leader makes leaders of those around him. Sexton knows how to call a move.
How he plays his hand as the new Ireland captain will play its part in how his legacy is framed.