A strong defense is vital to an NHL team's success. That's especially true during the Stanley Cup playoffs, when having a strong pair of defensmen can be as crucial as a top-scoring forward line or a reliable starting goaltender.
Every team employs varying defensive systems, depending in part on roster depth. The foundation of that system is the top pairing of defensemen. They're the two blueliners who tend to log the most minutes per game. They see action in five-on-five situations, on the power play and on the penalty kill.
Some teams may be stronger on one side of their blue line.