Djokovic hasn't recovered from the injury he aggravated in the Davis Cup, Fed is resting and del Potro has one eye on the Davis Cup final against Spain.
However, consolation lies in the fact that Rafael Nadal and Andy Murray, combatants in the Japan Open final, haven't bailed. And, with some of the big boys out, players chasing a spot at next month's World Tour Finals in London will have extra motivation.
Here's a look at the draw:
First quarter: Tough for Rafa
Last year during the Asian swing, Nadal played three straight weeks in Bangkok, Tokyo and Shanghai. Coming off a grueling summer, it seemed to make no sense. Apparently, Rafa felt bad for pulling out of Bangkok in 2009 and decided to make amends.
Well, he lost to fellow Spaniard Guillermo Garcia-Lopez in what will likely go down as the most wasteful encounter of his career. Nadal went an unbelievable 2-for-26 on break chances.
Nadal could face Garcia-Lopez in his opener, and this time it'd be easier. Garcia-Lopez, predictably, hasn't been able to back up his breakthrough 2010.
In a likely Davis Cup appetizer, David Nalbandian, known to sizzle in the fall, could confront Nadal. The best-of-three set-up should help the surgically repaired Nalbo, who realistically had no chance of topping the world No. 2 at the U.S. Open given the longer format.
Nadal, too, won't be lacking in motivation after getting bageled by Murray in the final set in Tokyo. He hasn't won a non-clay event in 2011.
Janko Tipsarevic, fresh off his first title in Kuala Lumpur, is one of those in the hunt for London. The Serb is in the same mini-section as Beijing winner Tomas Berdych, but that won't worry him, since he's 4-0 against the Czech. Berdych most likely confronts good pal Radek Stepanek in the second round.
Second quarter: Nico -- and a not-so-retired Roddick
Nicolas Almagro booking a place at the year-end championships? It could happen.
Almagro routinely shuns Rotterdam and Dubai to hit the dirt on the modest Latin American Golden Swing. His three non-clay quarterfinals in 2011 have come at two small events: Auckland, Kuala Lumpur and the Canadian Masters, where he got a nice draw. Had he made a commitment to apply himself on hard courts earlier in his career, who knows where he'd be.
Almagro likely starts with countryman Tommy Robredo, which he should get by, since Robredo has had another injury-ravaged campaign. A pity since he began '11 well.
A visibly annoyed Andy Roddick, who walked out of a news conference in Beijing after being asked whether he or Federer would retire first, might be charged up in Shanghai.
Roddick probably will be pleased about his section, landing qualifier Yen-Hsun Lu (hello, Wimbledon 2010) in the first round, a qualifier or Mr. Potential, Grigor Dimitrov, in the second and potentially Almagro in the third.
And who might Roddick battle in the quarterfinals? Third-seeded David Ferrer, whom Roddick beat at the U.S. Open.
Third quarter: Fish and Tsonga, again
Although Roddick's health has largely led to a forgettable season, close buddy Mardy Fish is having his finest campaign. Fish is looking good for London.
Fish had another solid week in Japan, reaching the semis, and given his form, you'd expect him to land in the quarters. It's either Kevin Anderson or Bernard Tomic following a bye. Fish downed Tomic in Japan and handled the improving Anderson (who has a banged-up knee) at Flushing Meadows. Marin Cilic also looms, and Cilic was boosted by his appearance in the final of the China Open, albeit aided by a helpful draw.
Fish's earlier-than-expected loss at the U.S. Open stung, since he was the American pre-tourney top dog, ahead of Roddick. How he'd like to get a rematch with conqueror Jo-Wilfried Tsonga, who prevailed in five sets in their ill-tempered fourth-round affair. Like Fish, if the season ended today, the Frenchman would be part of the elite London eight.
Fourth quarter: Dandy Andy?
The year-end championships are no doubt a prestigious event, and the tournament takes on extra significance if it's in your own backyard. Such is the case for Murray. He might rack up a few more sponsors if he wins it all.
It's mostly been a case of the same old for Murray away from the majors: Going deep in tournaments and playing the big three (when they're in the field) tough -- if not upending them. Murray played some of his best stuff after dropping the first set to crush Nadal this past Sunday for his 11th consecutive victory.
Nadal faded in Shanghai last season after his exertions in Thailand and Japan, so will the same happen to Murray?
Murray usually comes out on top against Gilles Simon, a player who has a similar game but isn't quite as good. In Bangkok, Murray was taken to three sets.
However, if fatigue does finally set in -- Murray won the doubles title with brother Jamie on Sunday -- this could be Simon's chance to pounce. He's also in the race for London.
Semifinal predictions: Nalbandian def. Roddick; Tsonga def. Simon
London-based Ravi Ubha covers soccer and tennis for ESPN.com. You can follow him on Twitter.