there is an entry draft which i believe only allows you to 20 or younger to get drafted into the NHL
seron blekie
No rookie since the NHL's inception has ever won the Hart Memorial Trophy (The league MVP trophy which was first presented in 1924) in his rookie year.
Alexander Ovechkin
You have to play one hole season, to not be a rookie anymore.
At the age of 31, Fabricio Oberto holds the record for oldest rookie in the NBA. Oberto played for the San Antonio Spurs.
After they complete one full NHL season.
saddle dome
Sergei Samsonov of the Boston Bruins.
36
Greg Palma
Montreal Canadiens
Lebron James