The Philadelphia Flyers showed the hockey world what a No. 1 defenceman meant in July 2012 when they signed then-Nashville Predators defenceman Shea Weber to a spectacular 14-year offer sheet worth US$110 million.

Letting Weber walk would've meant a haul of top draft picks for the Preds, but the club matched the offer and described it as "the most important hockey transaction in franchise history."

Teams that compete for a Stanley Cup without an elite defenceman such as Weber are almost non-existent these days, but this might just be one of those odd years when the trend is bucked — with two of the four teams remaining lacking such a player.

The Anaheim Ducks captured their first and only Cup in 2007 with a pair of future Hall of Famers at the top of their defence in Scott Niedermayer and Chris Pronger. There's no such player fronting this year's edition though; the Ducks defence is instead made up of a collection of well-rounded parts, including 25-year-old American Cam Fowler and the young core of Hampus Lindholm, Josh Manson, Sami Vatanen and Brandon Montour.

Fowler, who's absorbing almost 27 minutes per-game this spring, is the closest thing the Ducks have to that ace, but he's yet to top 40 points from the back-end in his seven NHL seasons — a touch below the current greats in that respect.

Pittsburgh, meanwhile, lacks anything close to the top-end No. 1 guy with Kris Letang shelved for the playoffs by a neck injury. The Pens are trying to go back-to-back for the Cup with a collective approach in his absence, doling out near-even minutes to their pack of six, which is generally led by former Oilers cast-off Justin Schultz.

Schultz, who left Monday's Game 2 against Ottawa with an undisclosed injury, has become an effective top-four option for Pittsburgh — he had a career-best 51 points this season — but he doesn't meet the all-situations requisite of that upper-class No. 1 defender. The Pens don't use him, for instance, on their penalty kill.

The Ottawa Senators don't just have that lead defenceman, but maybe the best one in the world at the moment in captain Erik Karlsson. The 26-year-old, a two-time Norris trophy winner as the NHL's best defenceman, has shredded foes during the playoffs, humming at around a point per-game while soaking up nearly 30 minutes every night.

Nashville has not one, but maybe two candidates in P.K. Subban, the former Norris winner who was flipped for Weber last summer, and Roman Josi, the Swiss defender who finished fifth in the Norris voting in each of the previous two seasons.

It's that defence, and the top of it especially, which makes the Preds such a threat to emerge with a first Stanley Cup next month.

Getting 16 wins without the defender who can kill penalties, run a power play, match up with top lines and drive an offence has shown to be highly improbable — bordering on impossible. It's just too many games at too high a level to survive most of the time.

Only two real exceptions exist since the 2004-05 lockout: The '09 Pittsburgh Penguins, who had Sidney Crosby and Evgeni Malkin at their physical peaks, and the '06 Carolina Hurricanes, who rode Cam Ward and Eric Staal to a first and only Cup.

2016 Pittsburgh Penguins — Letang: 15 points, 29 minutes per-game

2015 Chicago Blackhawks— Duncan Keith: 21 points, 31 minutes per-game

2014 Los Angeles Kings — Drew Doughty: 18 points, 29 minutes per-game

2013 Chicago Blackhawks — Keith: 13 points, 28 minutes per-game

2012 Los Angeles Kings — Doughty: 16 points, 26 minutes per-game

2011 Boston Bruins — Zdeno Chara: nine points, 28 minutes per-game

2010 Chicago Blackhawks — Keith: 17 points, 28 minutes per-game

*2009 Pittsburgh Penguins — Sergei Gonchar: 14 points, 23 minutes per-game

2008 Detroit Red Wings — Nicklas Lidstrom: 13 points, 27 minutes per-game

2007 Anaheim Ducks — Niedermayer: 11 points, 30 minutes per-game/Pronger: 15 points, 30 minutes per-game

*2006 Carolina Hurricanes: Bret Hedican: 11 points, 23 minutes per-game