World Tour Final is the most important tournament after 4 majors

Wertheim: "how many times Nadal has won the year-end shebang? (Hint: zero, because his body can't last the entire season, and durability is part of "greatness.")"
One of the biggest myths about Nadal is that his body is not durable and cannot last the entire season... and therefore he cannot show up or win the World Tour Finals year-end championships. This indoor championship is not just historically the fifth most signficant title in tennis (only after the four majors), it is the ultimate gladiatorial battle between the world very best players. Winnig the year-end championship thus validates the champion's greatness and domination over the year's very best players.
This excuse for Nadal fails the smell test. The facts indicate that the more logical reason why Nadal hasn't won it is because he is relatively incompetent on indoor hardcourts and uses 'injury' excuses to avoid this major event and downplay his losses. The facts are:
(a) In truth, Nadal has been a highly durable player. Nadal has already played 750 matches, the sixth most career matches among all active players. The top five players on the list are all at least 31 years old: Nadal just needs 71 more matches to tie Tommy Haas for second place! Nadal is very durable when he chooses to be: his 'lack of durability' rarely appears during the clay season (except when he loses, and then he uses injury as the excuse).
http://tinyurl.com/awagp2c
(b) Yet, despite his continual whining about being injured, Nadal has never had surgery for any injury in his career (unlike many other more seriously-injured players), indicating that none of his injuries and injury breaks have been really that serious. It's more plausible to consider that, since 2005, the very smart Team Nadal has been making Nadal take preventative shut-downs during undesirable periods of the season (on surfaces he is likely to incur losses). If Nadal had showed up for more indoor events -- like Federer did for clay events -- Rafa might have lost more matches to Federer.
(c)  Nadal's World Tour Finals win-loss record is an abysmal 9-10 (47%) -- and that's when he showed up most-prepared to compete. Nadal was absent in three different years -- had he showed up he probably would have had even more losses against the world's top 8 players who were mostly hardcourt specialists.
(d) Nadal's worst surface is indoor hardcourt: deducting Nadal's 9 indoor clay wins, his indoor hardcourt/carpet win-loss is ony 47-29 or 61.8% for around 60th place in the ATP era. The more versatile Federer's worst surface clay is still 77%, good for 11th in ATP era (Federer has reached 23 clay finals, winning 10 clay titles).
(e) How can Nadal qualify for greatness if he is relatively incompetent on indoor hardcourts? All the GOATs in tennis history were great indoor players, and tennis the game has its roots from the indoor game played centuries ago. Even clay king Bjorn Borg found a way to win 23 hardcourt/carpet titles, including three (3) year-end championships. Nadal's lack of success on indoor hardcourts is a red flag on his GOAT aspirations.
In 2008 Fall, Nadal skipped the World Tour Finals (Tennis Masters Cup) in Shanghai citing fatigue. One week later he skipped the Davis Cup Finals in Argentina claiming his knees were injured.
- Nadal cited fatigue as his reason for skipping the 2008 WTF. Yet in his previous two indoor tournaments in October (Paris Masters, Madrid Masters were his only events after the 2008 US Open) he played doubles with Juan Monaco and Carlos Moya each time -- so obviously he wasn't that tired, or he would not have played doubles both times. Perhaps the real reason he stayed away from was that -- after losing to Gilles Simon in Madrid and Davydenko in Paris -- then No. 1 Nadal realized he had lost form since the 2008 Olympics and was likely to fail at the World tour Finals. So he stayed away rather than risk 2 to 3 losses in the WTF round robin tarnishing his image of invulnerability. [Compare Nadal's attitude with Federer, who has played two away Davis Cup ties in Australia which is a much longer travel distance: days after losing a heart-breaking US Open semifinal to Djokovic in 2011, Federer traveled to Sydney to battle Hewitt and Tomic on Australian grass in the middle of the hardcourt season.]
- in his entire career, Nadal has never ever bothered to travel for an away Davis Cup tie outside Europe, not even for critical ties against USA or the DC Finals. After claiming to be fatigued one week before the WTF, Nadal later claimed his knees were injured so he couldn't fly to Argentina to play the Davis Cup Finals. Meanwhile, on the eve of the Davis Cup Finals, Davis was seen vigorously playing water sports (water skiiing, doughnut boat, etc.) in a luxury Mauritious resort (see link for photos). Obviously his 'injured knees' were not so injured that it immediately required intensive treatment and rehab.
http://tinyurl.com/crhtg92

http://sportsillustrated.cnn.com/tennis/news/20130612/rafael-nadal-roger-federer-french-open-mailbag/