A friendship that has endured decades and survived the partisan divide of international sporting competition now faces surely its greatest test at the Ryder Cup.
Davis Love III and Darren Clarke are close, at ease in one another's company and always ready to share a laugh and a joke.
But at Hazeltine this week, there will be a chasm between them as they captain their respective teams in the heat of battle.
While they have played on opposing teams in the past, even directly against one another, this dynamic represents a whole new ball game.
Love carries the double burden of expectation and something bordering on desperation. The United States are favourites, which brings the expectation, and yet they have not won it since 2008 - desperation.
He knows only too well the pain of failure in this competition, having been at the helm for the 2012 edition. What the Europeans gleefully recollect as the Miracle at Medinah might more appropriately be titled the Meltdown at Medinah on American shores.
At 10-4 up on the Saturday, the tributes to Love's captaincy were flowing freely. He could do no wrong. Until he did.
Europe stormed back, taking the final two points up for grabs in the four-balls before winning Sunday's singles session 8.5 to 3.5. Victory was theirs. Love suddenly had a lot of questions to answer.
A man defined by his laid-back manner became a little more uptight, his captain's picks coming in for particular scrutiny after one of them - Steve Stricker - lost the decisive match to Martin Kaymer and sealed an 0-4 record in Illinois.
That chastening experience lingers over Love in Minnesota this week. Lessons must be heeded, because the USA have by now more than enough first-hand knowledge of defeat to know its consequences.
Clarke is largely untroubled by such knowledge, having enjoyed victories in four of his five Ryder Cups as a player, and twice as a vice-captain.
He has long been cast in the role of one of golf's good guys. Avuncular and rarely seen without a smile, Clarke's 2011 Open Championship win was more warmly received than most.
But he need only look across at his opposition and the drubbing they suffered last time out to know that nice guys don't always make great captains.
Even Tom Watson, a cherished institution of the sport, could not escape the damning assessments that follow a Ryder Cup loss.
Phil Mickelson, back at the event this year for an 11th appearance, laid bare his disenchantment with Watson's captaincy after that 2014 humbling when the veteran sat just down the table from him at a memorable media conference that bore more resemblance to an autopsy on a live body.
The thought of Love or Clarke having to face similar probing and scrutiny from within their own ranks following Sunday's final reckoning is a painful one for those who have respect for the two of them, which is just about anyone who has ever watched the game of golf.
But reputational damage is a hazard of the job of captaincy and one of them will suffer a blow this week. One would wager, though, that the other will be on hand to cheer them up. That's what friends are for.