I have a few general rules when it comes to building a team in a fantasy hockey keeper league. One of the more important ones is to not plan beyond a two or three year window. You are not building a real NHL club, and too often fantasy hockey poolies place an emphasis on youth and prospects over proven veterans with gas still left in the tank. So using my general rule, take a look at your team(s). Can you realistically say you will have a shot at winning the league at some point within the next two or three seasons? If not, time to scrap the rebuild and start adding proven NHL talent.
Keeping my rule in mind, I have compiled a list of the top 10 keeper league defensive prospects to own (assuming standard keeper league rules and scoring categories). Using the two or three season scope, I balanced the long-term upside of these players with their NHL readiness. The cut-off point for this list is 25 games played at the NHL level. Erik Karlsson is a player who would have cracked the list (and maybe topped it as well), but he has played more than 25 games with Ottawa.
This list is in order, so I probably wouldn't trade the fourth player straight across for the fifth player, and so on. I balanced talent with opportunity, as it takes both to become an elite offensive defenseman in the NHL.
I have also included a stylistic comparison for each player. Don't get insulted if I have compared an unproven prospect to your favourite current or former NHL superstar – I am just comparing playing styles.
My previous lists:
Top 10 Keeper League Centers
Top 10 Keeper League Left Wingers
Top 10 Keeper League Right Wingers
Top 10 Keeper League Defensemen
Top 10 Combo Players (Points + PIM)
Top 10 Keeper League Goaltenders