
Extract the answer to the question from the following context.
Question: What type of players are in the NHL?
Context: The Flying Fathers, a Canadian group of Catholic priests, regularly toured North America playing exhibition hockey games for charity. One of the organization's founders, Les Costello, was a onetime NHL player who was ordained as a priest after retiring from professional hockey. Another prominent exhibition hockey team is the Buffalo Sabres Alumni Hockey Team, which is composed almost entirely of retired NHL players, the majority of whom (as the name suggests) played at least a portion of their career for the Buffalo Sabres.

professional
