The responsibilities a defenseman faces are numerous. He has to be strong in his own end to prevent goals, make smooth passes out of the defensive zone and chip in offensively by getting pucks to the net. The best blueliners also have to be able to play large amounts of ice time in all situations.
The winner is selected in a poll of the Professional Hockey Writers' Association and will be announced at the 2012 NHL Awards Show on June 20 at the Encore Theater at Wynn Las Vegas.
At age 35, Chara had his best offensive season with 52 points, fourth among all NHL defensemen. He played 25 minutes per game and led all defensemen -- and was third in the League -- with a plus-33 rating. He also brought a physical presence, using his 6-foot-9, 255-pound frame to lead the Bruins with 166 hits.
Chara also had 12 goals -- including eight on the power play -- played his 1,000th NHL game in March and was named a captain at the 2012 All-Star Game, his sixth All-Star appearance.
This marks the fifth time Chara has been a Norris finalist. He won the award in 2009, finished second in 2004, and was third in 2008 and 2011.
"It's been a pleasure and an honor getting to play with one of the best, a guy who I think should go down as the best defenseman ever," teammate Tim Thomas told ESPN.com. "Certainly, in his own way, there's been nobody like him in the NHL. Nobody brings the exact attributes that he brings, so I count myself lucky to have been playing with him and behind him."
Karlsson had one of the best offensive seasons by a defenseman in recent memory. He was tied for 10th among all players in the League with 78 points, the most by a blueliner since Detroit's Nicklas Lidstrom had 80 in 2005-06. He led all NHL defensemen in goals (19), assists (59) and points. He tied the Senators' single-season club record for goals by a defenseman, while his assists, points and five game-winning goals set new team records.
Not only did Karlsson star offensively, he was a plus-16, second on the team and a huge turnaround from his minus-30 last season. He also led all defensemen with 67 takeaways. And he did it while playing a career-high and team-leading 25:19 per game. He also played in his second straight All-Star Game.
Thanks in part to Karlsson, the Senators rose from 13th in the Eastern Conference in 2010-11 to eighth this season.
Karlsson is the first Senator to finish in the top three in the Norris voting since Chara finished second in 2004.
"We wouldn't be where we are right now without him," goalie Craig Anderson said of Karlsson earlier this season. "I can't say that for any other defenseman in the League right now -- that their team is so dependent on one player. Not that we rely on just one player, but in the grand scheme of things, he is our Sidney Crosby or whatever you want to call him for our team."
Weber was just as important for the Predators this season. He tied Karlsson for the League lead among defensemen with 19 goals, and his career-best 49 points tied for sixth in the League. His 10 power-play goals were the most among defensemen this season.
The workhorse and team captain was fifth in the League in ice time per game at 26:09 while posting a career-best and team-high plus-21 rating and finishing second among all blueliners with 51 takeaways. He quarterbacked the League's top power-play unit and also played more than two minutes per game shorthanded. Weber used his 6-4, 232-pound frame to punish the opposition, leading the team with 177 hits and blocking 140 shots. And he did all that against the best the opposition had to offer -- he tied for the team lead and tied for 16th in the League in advanced-metrics website Behind the Net's Quality of Competition rating, a number generated by the average relative plus/minus rating of opposing players based on head-to-head ice time.
With Weber, the Predators finished in the top 10 in the League in goals-for and goals-against, and had their best season since 2006-07.
"I think in terms of his game, it's raised in the sense that he's always been good offensively and he's always been physical and all that," Predators coach Barry Trotz told NHL.com. "Where he's raised his game is he's more comfortable as Shea Weber as an elite player in the National Hockey League. A lot of players make the statement the player has arrived. Well, he has arrived. He's arrived not only as a player, he's done that the last few years, but he's arrived as an elite player in the League and an elite leader."
This is the second straight year Weber is a Norris finalist; he finished second last year to Detroit's Nicklas Lidstrom. He also finished fourth in 2009.
Contact Adam Kimelman at firstname.lastname@example.org. Follow him on Twitter: @NHLAdamK