FIFA President Sepp Blatter says tiredness after a long season is a factor in the World Cup losing top players to injury.
Blatter tells reporters that it's "too long a season and always the same players are always in the same competitions."
"Now they are tired," the FIFA chief says.
France winger Franck Ribery and midfielder Marco Reus of Germany dropped out in recent days.
Portugal superstar Cristiano Ronaldo has missed warm-up matches due to persistent left leg injuries, and Argentina's Lionel Messi has seemed below full health.
Blatter suggested after the 2010 World Cup that the long European season was a factor in producing too few entertaining matches.