‘Under the player development contract, a prospect cannot play in the NHL’s top minor league until he turns 20 years old or plays four years of major juniors. Cozens won’t turn 20 until February 2021 and has played only three full seasons in the CHL’s Western Hockey League, which ensures he will return to the Lethbridge Hurricanes if he’s unable to make the Sabres’ roster next season.’
Sabres' Dylan Cozens unable to play in Rochester because of NHL, CHL agreement
Source: Buffalo News