at the top of the game

08:05 Oct 14, 2010 

I read this often in sports articles (Canada), and in that context I always read it as that "they are currently playing at their highest level/full capacity (i.e. conditioning, focus,..), not that they are the best in the sports they play.
Proof would be that it is often used in texts talking about players who are not the best in the sport, but eg. a couple of weeks into the season, the writer would say "he is at the best of his game now."
"Calderon played a lot of meaningful basketball in a starting role. He will be at the top of his game come November."
"Silva is virtually unstoppable when he's at the top of his game."