Ci talk:1004671292
A 国手 is not necessarily a winner of a national championship.
Example: 我弟弟当选国手,我比自己当选还高兴。 (You don't select someone to be a national champion.)
A 国手 is one of the nation's top athletes, but not necessarily the national champion.
A 国手 can also be one of the nation's top doctors or chess players, according to dictionaries.