"A man's got to know his limitations" - Callahan, Magnum Force
When Matt O'Connor was taken out by a Blue bullet two years into his three-year contract, Leinster weren't exactly blessed with an immediate successor back in 2015.
The timing couldn't have been worse.
The World Cup was on the horizon and many prospective coaches were either tied up or just not interested enough in what was perceived to be a dying giant. From the outside, it did not look all that appealing as the golden generation had moved into retirement, Brian O'Driscoll hanging up his boots in 2014 and Leinster looking under-manned in Europe.
Eras end. That has always been the way. It is what you do when it happens that matters most. Look at Bath in England. They have not won the Premiership since dominating domestically in the early 1990s.
Look at Leicester Tigers. They were in their pomp in a seven-year stretch between 2007 and 2013, winning the Premiership four times, making the final on the other three occasions.
Since then, there has been nothing to shout about, getting to the semi-finals three times, but no further.
Look at Toulouse. They bridged a seven-year gap to their last French championship in 2019 and it has been a decade since the last of their four European Cups in 2010.
It was left to Leo Cullen to assume the mantle of the Leinster lead role, with just one year as a forwards coach for reference.
Graham Henry was employed as a consultant to provide insight, wisdom and plain practical advice on how Leinster could move forward.
It is fair to say Leinster would not be where they are today without Cullen. He cared enough to step up when he knew he wasn't really ready and soon realised his limitations, in terms of experience.
Europe has always been where Leinster take their temperature and they went cold to finish bottom of their Pool in a disastrous campaign.
Okay, the province finished top of the PRO12 in 2016 only to be humbled by Connacht in the final at Murrayfield.
They do say you learn more from failure than success.
The commitment was made there and then to break with the nod to experience over youth and Cullen has not taken a step back from that since.
The coach was also intimately aware of the talent percolating away beneath the surface as Robbie Henshaw moved East from Connacht, Tadhg Furlong and Garry Ringrose continued to grow and the precocious James Ryan was about to land.
An absence of ego is, perhaps, Cullen's greatest trait and, one season later, he resolved to bring Stuart Lancaster on board in September 2016 in the single smartest move of his tenure.
It has evolved into a marriage made in rugby heaven, Lancaster rehabilitating his torn reputation on the pitch with Cullen calmly overseeing the creation of a new era.
In three years, it has become a place where seekers from all over the globe, and other sports, flock to find out the secret to their success.
It is also a place where coaches come now.
Felipe Contepomi rejoined his old club as backs coach in 2018, Cullen and Lancaster extended their contract last summer and the vastly experienced Robin McBryde moved from Wales to Dublin after the World Cup in November.
It was just last week when Lancaster spoke of his argument for greater continuity of selection against Cullen's relentless push to rotate in the name of opportunity.
The crazy competition for the shirts comes in tandem with the healthy back-and-forth between the coaches - all of the coaches.
"It's diversity. It is hugely important," said Cullen.
"Even with Felipe coming in last year, those fresh eyes on the group, and Robyn coming in this year, it's hugely important for us to be able to see things in a different light.
"As a coaching group, those guys have a tonne of experience that I don't have, so I lean on that all the time."
The man knows his limitations and accounts for them.