It is the season of the rookie in the NHL, and not just because of high-scoring forwards like Toronto's Auston Matthews and Winnipeg's Patrik Laine, or Pittsburgh goalie Matt Murray. The biggest surprise of this season is how eight teams are using rookies on their top defensive pairing.
Looking back through recent history, it is unusual for there to be more than one or two particularly exceptional defensemen to play on the top pair in their rookie season. In 2015-16, for example, there were only occasional stretches of the season when rookies like Carolina's Jaccob Slavin, Edmonton's Darnell Nurse and Philadelphia's Shayne Gostisbehere were on the top tandem. Right now, there are eight rookies being employed on the main duo.
Not every team is using a rookie defenseman in the top two for the same reason. Some teams are blessed with one of those rare and particularly talented prospects, like Zach Werenski of the Columbus Blue Jackets, while other teams have an elite veteran who is capable of guiding a young apprentice, like Drew Doughty of the Los Angeles Kings or Zdeno Chara of the Boston Bruins. Some teams have been hit with so many injuries that they are left with few alternatives, like the Vancouver Canucks.
Here's a ranking of the eight rookie defensemen being used on the top unit this season, and how they have fared so far: