I am reading this post http://www.javacodegeeks.com/2013/06/parsing-espn-api-using-java-and-google-gson.html
The NBA request http://api.espn.com/v1//sports/basketball/nba/athletes?apikey=KEY
returns only 50 athletes, you have to use the offset parameter to get more
http://api.espn.com/v1//sports/basketball/nba/athletes?apikey=KEY&offset=51
So in your case
http://api.espn.com/v1/sports/golf/athletes?&apikey=KEY&offset=51
I am still reading the post but now I see I can return more players and the first request only got to players last name ending with B so geeze to get all athletes the JSON response would be huge!
I can't find this on the ESPN docs, so I don't know how developers are supposed to know this, there may be a better way but at least now I know how to get all the players.