Once upon a time, the Boston Bruins were looked at as a team that was carried by great goaltending and a stingy defensive system deployed by Claude Julien. When people talked about the personnel at forward, it wouldn't be a surprise to hear things like "no true #1 center" or "they have two 2nd lines". This season, that couldn't be further from the truth. In fact, you could make a decent argument that based on Even Strength points per 60 minutes, the Bruins have had the BEST forward line in hockey this season.
Through 36 games, the Bruins top line has 3 players in the top 12 in ES P/60 (minimum 20 GP). Brad Marchand leads the league in this category at 3.34, Tyler Seguin is 8th at 3.04, and Patrice Bergeron is 12th at 2.83. That's pretty good work for what in the past has been looked at as a really good second line. The Bruins forwards also have the depth to go with that elite line.Rich Peverley is 17th (2.77), Milan Lucic is 42nd (2.47), Chris Kelly is 55th (2.35), Krejci is 67th (2.20), and Nathan Horton is 100th (2.04). Benoit Pouliot is the only Bruin forward in the top 9 who is outside of the top 100 (204th at 1.48), but two of the Bruins 4th liners (Paille and Cambell) can be found in the top 150. That just happens to be higher than Ilya Kovalchuk, Bobby Ryan, Danny Briere, and Mike Richards.
So while the Bruins deservedly get credit for having two outstanding goaltenders, and quite possibly the best defenseman on the planet in Zdeno Chara, they've very quietly assembled a group of forwards that is very effective at both carrying out defensive responsibilities and contributing to the scoresheet at even strength. That all adds up to by far the best goal differential in the league and a real serious shot as repeating as Stanley Cup Champions.