Defending champions Japan are missing most of their foreign-based stars. Fulham midfielder Junichi Inamoto broke his leg in the draw against England, while Bologna's Hidetoshi Nakata has a long-standing groin injury. In-form striker Tasuhiko Kubo is the latest withdrawal, because of a knee problem.
Meanwhile Feyenoord's Shinji Ono and Germany-based Naohiro Takahara are being kept back as overage players at the Olympics.
It's easy to look at the list of missing players and think how much better Japan's Asian squad can be, but the fact is they could still be good enough to retain the trophy. With any other country, the absent stars would be considered a major weakness, but the advantage of Japan having so many European players, is that the 'second team' has had plenty of international experience, too.
Of the top teams, Iran are probably the closest to being at full strength. Under-23 captain Moharram Navidkia, is out for six months after knee surgery, an injury suffered during the Olympic qualifiers in May. He'll be missed more than Bayern Munich-bound Vahid Hashemian who rarely makes himself available for the team. The return of Branko Ivankovic, the Asian Games winning coach should stabilise the team somewhat, but the Croat knows the problems he faces when taking Iran to a major tournament. Iran's players can get unhappy during long periods away from home and the squad has a tendency to split along regional and club lines. The so-called superstars don't always get on as well as they should. Ali Karimi and Ali Daei were at odds during the 2000 Asian Cup, and the extent of Daei's influence on team selection has been criticised in the past.
Oman might not have much of a pedigree in Asian football, but they have improved enormously, thanks to one of the most astute European coaches to work in the Gulf. Milan Macala had enormous success with Kuwait, and followed it up by beginning Oman's brief revival in 2001, when he guided them to the final round of World Cup qualifying for the first time. He returned to take charge of Oman's Olympic side in 2003. They baffled Japan in the opening round of World Cup qualifying in Saitama, losing to a single injury-time goal.
Thailand, however, are a shambles. Since the end of Peter Withe's reign, which saw the best side in Southeast Asia finally break through at the continental level, things have gone from bad to worse. New coach Chatchai Paholpat has inherited a squad with discipline, morale, injury and fitness problems.