Last I counted we had 13 players over the age of 30 and a lot of those are well over 30. We've got a bunch of players who are 34,35, 36 etc.
Players can & do play well into their 30s, Ovechkin is still playing at the top of the NHL and he's around 37/38. However some performance drop off is inevitable. So having an ageing core of players means the team will struggle when up against younger, faster, sharper teams. Just on injuries alone, players in their 30s are more prone to injuries and take longer to recover.
Going forward the Devils need to recruit a younger team.
