Contender kryptonite: Biggest weaknesses on NHL's top 20 teams

The addition of Ryan McDonagh, right, shored up the blue line for the Lightning. But problems on the penalty kill remain. Kim Klement-USA TODAY Sports

No matter how good a team may be in the regular season or how blazing hot they get down the stretch, one nice thing about being an NHL fan is there is enough parity in the league that every team feels it has a chance come playoff time. On the other side of that coin, every fan base is also nervous heading into the postseason because there are no perfect teams.

With that said, let's have a look at one key weakness that each of the clubs currently in playoff position -- along with those still in the race -- will either have to correct as they head into the playoffs, or that could derail a trip to the Stanley Cup Final.