Roger Federer and Jack Nicklaus dominated their sports with talent and extraordinary mental toughness. Photo / AP
So Roger Federer is undisputed as the greatest (male) tennis player of all time, agreed?
His 19th major title at Wimbledon last weekend surely confirms that, and even if you remain a Laver/Nadal/Sampras fan, bear with me.
Rafael Nadal is second on the all-time list, with 15 slams, Pete Sampras is third on 14, Novak Djokovic fourth on 12. You might have a soft spot for the baseline brilliance of Bjorn Borg and his mastery of clay and grass in his 11 majors.
Only seven men have won all four grand slam titles. Federer's split is eight Wimbledons, five each from Australia and the US Open and a solitary French crown, in 2009.
So for the sake of this argument, humour me: Federer is top, the GOAT of men's tennis.
(Serena Williams' 23 titles mark her as perhaps the best of all, men and women, but for today, hold that thought.)
But is it possible to compare the greatest tennis player with the finest golfer?
Different fields of play, different implements, but perhaps the closest of individual sports in trying to sort this particular question, and obviously discounting automatically anything which involves subjective judging.
So here's the question: Is Federer's achievement greater than that of Jack Nicklaus?
It's tempting to say it's not quite apples vs apples, but let's persevere.
Federer has won his titles in arguably the strongest age of tennis. Since he won his first grand slam, Wimbledon in 2003, three men have dominated the game. Other major winners in that period are Andy Murray and Stan Wawrinka (three each), Marat Safin (two) and Andy Roddick, Marin Cilic, Juan Martin del Potro and Gaston Gaudio (one each). Talk about a closed shop.
You could argue the age of Borg, Lendl, Connors and McEnroe in the late 1970s-early 1980s surpassed it, but for sheer, stunning mano a mano contests, the last few years surpass that.
His ability to play beautifully, and without seeming to sweat, gives him an almost unreal quality at times. He has had to outlast, out-shoot the best of his opponents. In the mental department, he has been near-unbeatable.
Unlike Nicklaus, his success has come in an often claustrophobic environment. On the score of fitness, Federer clearly has it over golfers.
And what of Nicklaus?
In his favour, he was runner-up in the majors 18 times to Federer's (so far) 10. His spread of majors was 24 years from 1962 to that unforgettable 1986 Masters, aged 46. Federer's major spread is 14 years.
In terms of mental strength, Nicklaus was formidable. In a way, not dissimilar to Tiger Woods in his pomp, you sensed rivals were cowed, not believing they could win.
Nicklaus had that fierce concentration as he hunched over a putt. He also had to put up with the sneering fans in his early years. The contrast between the pudgy Nicklaus and the charismatic Arnold Palmer could scarcely have been more pronounced. Doubtless it hardened his resolve.
Just five players have won all four golf majors - Nicklaus won six Masters, four US Opens, three British crowns and five US PGA titles - the others being Woods, Ben Hogan, Gary Player and Gene Sarazen.
But a golfer has time to stop and smell the flowers, if you will, during a round; can play, within reason, when he or she is ready. Federer doesn't have that luxury.
Golf has different, more measured pressures. The eerie silence surrounding the 18th green with a 10-footer to win a championship no doubt can rattle the nerves. Which is why Nicklaus, and for a time, Woods were so good. They were supreme at shutting out distractions.
Neither player has all four titles in a calendar year, although Nicklaus won three in succession in 1971-72; Federer won three in a year three times, 2004, 2006 and 2007, being tripped up on French clay each time.
One final point: tennis players must beat an opponent on the other side of the net; golfers essentially play themselves. Therein lies one distinction.