Golf's elite, headed by Tiger Woods and Rory McIlroy, will face the year's most stressful challenge when they assemble at Augusta National this week for the US Masters. To borrow the wonderfully convoluted words of Donald Rumsfeld, it has to do largely with known knowns and known unknowns which have captured their imagination since childhood.
As American sports psychologist Dr Bob Rotella put it: "It's a wonderful course to play golf on and it's there to be had, if you can let yourself have it. But guys know that winning it will mean being invited back forever. And there can be such an urge to get everything perfect, that you screw it up."
For the first time, Ireland will have five representatives. McIlroy is joined by Graeme McDowell, Pádraig Harrington, Darren Clarke and last year's British Amateur champion, Alan Dunbar, who will be turning professional immediately afterwards.
"From the time I saw Tiger on TV chipping into the 16th hole when he won in 2005, the Masters has stuck in my mind," said Dunbar. "Since then, I made a point of watching it every year. Now I'm about to realise the dream of playing there. It's an amazing opportunity."
McIlroy would be forgiven for failing to share this enthusiasm after a decidedly troubled build-up to the event. It is hard to recall any player being subjected to such relentless scrutiny, on and off the golf course, as the Holywood star has had to endure this year.
Most of it has involved seriously hare-brained analyses of his swing by observers who, frankly, are not qualified to make such judgements. Indeed the one occasion, at Doral, where the player explained what had gone wrong with his technique was reported incorrectly, according to his coach, Michael Bannon.
McIlroy undoubtedly erred in planning his schedule for the year so far. Crucially, he failed to take on board the difference he would experience in adjusting to new Nike clubs in competition, as opposed to the practice ground. And he has since acknowledged this error.
As to the number of tournaments he plays in the build-up to the Major championships, only he can know. And recent experience would suggest that it's something he's trying to figure out by trial and error. In the meantime, a dent to his confidence and losing his status as world number one can both be put right with a solid performance this week.
Rotella, who guided Mike Weir (2003) and Trevor Immelman (2008) to success at Augusta, will have Harrington and Clarke among his clients and may also work with McDowell. Against this background he is fascinated by the extent to which the build-up is dominated by talk of a Woods-McIlroy showdown.
"That's fine for the public but I don't see the two players buying into it," he said. "Tiger and Rory are smart enough to know they've got to play against themselves on the golf course. If the world wants to make it a big thing, let 'em. But the two players will be thinking that if they play the way they know they can play, they'll win the tournament. A difference would be if they got paired together at the weekend, when greater discipline would be required to retain focus.
"I don't think Rory is ever going to be afraid of Tiger, no more than Tiger is ever going to be afraid of Rory. They're very different people. Tiger is so single-minded about what he wants that it's hard to imagine him caring that much about Rory. Rory on the other hand cares about everybody. I think he's a great, down-to-earth kid. That's what makes a prospective duel between them so intriguing.
"Historically, older players find it easier to be friendly with players 10 or 15 years younger than them. There isn't the jealousy or envy that would have been fostered by playing against each other as kids. And while you could argue that Tiger might see Rory as someone standing between him and future Major wins, he could also view Rory as someone who could force him to become a better player. And I imagine that's the way Rory thinks about Tiger."
On the question of self-imposed pressure for the average challenger at Augusta, Rotella said: "It's amazing to see the way some guys behave in the practice area. They become panicky about the state of their game, over-reacting to everything. On the putting green, a missed four-footer they wouldn't have noticed a few weeks previously suddenly becomes an issue."
So to the known unknowns. Seasoned campaigners go to Augusta each year looking for subtle changes aimed at catching them off guard. Like a mousetrap being continually upgraded to cope with more sophisticated mice. I remember Bernhard Langer making such claims 13 years ago, though the course betrayed no obvious sign of change from the previous April. "The fairways are narrower and they've put a lot more sand, soft sand, in the bunkers," Langer insisted. "In both cases they want to ensure the ball doesn't spin, which is going to make it a lot more difficult going into hard greens." Could this be true? When Langer's observations were put to a green jacket, he eventually conceded: "Certain areas might be a little tighter, but no more than a yard – honest."
Clearly there's a balance between carefully assessing the challenge and overdoing it. But nobody would argue with the words of 1948 champion Claude Harmon, who said: "Reading an Augusta green is like reading the small type in a contract. If you don't read it with painstaking care you are likely to be in trouble."
In the light of subsequent events, one of the most fascinating exchanges I observed at Augusta occurred in the media centre on the Tuesday of Masters week in 2004. When interviewer Billy Morris read out Phil Mickelson's impressive record of seven top-10 finishes in 11 appearances, the player responded: "But no wins. No wins." Then, pointing to Morris's jacket, he caused much laughter by adding: "I want what you have. I want one of those. Those are nice."
Five days later, Mickelson had won his first of three green jackets. And it is equally fascinating that in the same interview with Morris he recounted how he had spent Monday and Tuesday of the previous week trying to find areas in his game "where I can just save half a shot to a shot a round". This had been prompted by the discovery that saving a stroke a round would have earned him two wins and a tie in his three previous Masters appearances. The margins are that fine.
Which goes some way towards explaining why rookies don't do especially well at Augusta. And why power and a strong short-game offer glorious possibilities on this lush, undulating terrain with remarkably accessible par fives.
Where, you may ask, does the Woods of today fit into all of this? Very comfortably, is the answer, especially in the light of three tournament victories already this year.
Those who would downplay his prospects of future Major successes point to the fact that it is almost five years since he won the last of them, even further back than Harrington, who continues to generate much comment in this area. But in the 18 Majors he has competed in since capturing the US Open at Torrey Pines in June 2008, Woods has had five top-four finishes including a share of fourth place behind Mickelson at Augusta in 2010 and Charl Schwartzel in 2011.
Despite his various tournament successes during this period, however, a question mark remains. And it won't be removed until he manages to secure Major number 15, which could come this week if his mind permits it.
There's a lot of different ways of winning the Masters, which Schwartzel proved with four finishing birdies and Bubba Watson illustrated with an astonishing wedge down the 10th in last year's play-off. An easier, scoring set-up on the back nine in recent years has made it much more of a Sunday competition than it had previously been.
As for Irish prospects, it will be more a test of McIlroy's mind than his undoubted skill, given everything that has happened in the eight months since that marvellous eight-stroke triumph in the PGA Championship at Kiawah Island. On more recent form, McDowell looks to be a strong challenger, though he has missed three cuts in five Masters appearances and has a best finish of tied 12th last year.
"If I was looking for a winner, I would be thinking of guys who can go there and feel good about their putting and just play," said Rotella. "Guys who putt great at Augusta are guys who believe they can make any putt on six or seven different lines. Those who don't are the guys who see the greens as being so perfect that they screw up their chances by seeking putting perfection."
Greg Norman was such a Masters perfectionist. Too late, he finally became aware of this crippling truth when, looking at playing partner Jose-Maria Olazabal walk up the 18th towards a second Masters title in 1999, he found himself thinking: "It's as easy as that. He's won the tournament."