Defense changes will be upgrades for Coyotes, Oilers

Defense is one of the most difficult positions for teams to improve quickly. Good prospects can be hard to identify and take years to develop, and acquiring established defensemen through trade or free agency can be costly.
During the offseason, the Arizona Coyotes, Edmonton Oilers, Florida Panthers and Nashville Predators paid that premium in order to take significant leaps forward on defense. In each case, these investments could prove fruitful.

Defensemen also have been the most difficult to evaluate statistically, because there are no metrics that measure goals prevented. But various ways to measure a defenseman's performance have been developed by studying the player's impact on his team's results relative to what was expected, based on the zones and man-power situations in which he was deployed, and against which opponents.
Armed with these new metrics, it's possible to identify the four teams who have made the most significant improvements to their defense group, and to break down their potential impact.

Arizona Coyotes

When Coyotes general manager John Chayka was hired May 5, one of his top priorities was upgrading Arizona's defense.
The Coyotes acquired impending unrestricted free agent Alex Goligoski from the Dallas Stars on June 16 in a trade for a fifth-round pick in the 2016 NHL Draft, and six days later, Goligoski signed a five-year, $27.375 million contract with the Coyotes (average annual value $5.475 million).
Like his new teammate Oliver Ekman-Larsson, Goligoski is a complete, two-way defenseman who can play tough minutes against any opponent in any zone and in any man-power situation, and give the Coyotes an edge in scoring and shot-based metrics.
During the first round of 2016 draft, the Coyotes traded the 20th pick and center Joe Vitale to the Detroit Red Wings for the contract of center Pavel Datsyuk and the No. 16 pick in the draft. Arizona then used that pick on defenseman Jakob Chychrun. The next day, the Coyotes acquired defense prospect Tony DeAngelo in a trade with the Tampa Bay Lightning for the No. 37 pick in the draft.

The Coyotes then signed unrestricted free agent defensemen Jamie McBain on July 1 and Luke Schenn on July 23.
Goligoski will have the greatest individual impact, but the infusion of defensemen should help transform Arizona's group into one of the League's best.

Edmonton Oilers

The question isn't whether the Oilers improved their defense this season, but whether it came at too great a cost.
In acquiring Adam Larsson in a trade with the New Jersey Devils on June 29 for forward Taylor Hall, Edmonton gave up a player whose scoring and shot-based metrics suggest Art Ross and Hart Trophy potential in his future.
The trade occurred four days prior to the 10th anniversary of when Edmonton traded Chris Pronger to the Anaheim Ducks, on July 3, 2006. Since then, the Oilers have had a shortage of quality defensemen that has forced them to move players further up the depth chart than they would have liked, and they have missed the Stanley Cup Playoffs every season since.
If the addition of a top-pair defensive specialist like Larsson can reverse that trend, then no price was too great. With the return of Oscar Klefbom, limited to 30 games last season because of injuries, and the continued development of younger players Darnell Nurse, Brandon Davidson, Jordan Oesterle and Griffin Reinhart, the Oilers have everything they need to construct their best defense corps in 10 years, and for many seasons to come.

Florida Panthers

When the puck dropped to open last season, the only Florida Panthers who remained from the previous time the team made the playoffs in 2011-12 were defensemen Brian Campbell, Dmitry Kulikov, and Erik Gudbranson. One season later, they're all gone, too.
New Panthers GM Tom Rowe overhauled the defense. But how much did it actually improve?
The answer lies in a close examination of the most noteworthy addition, Keith Yandle, acquired from the New York Rangers in a trade for a 2016 sixth-round pick and a conditional fourth-round pick in 2017 on June 20. Yandle then signed a seven-year, $44.45 million contract with the Panthers (AAV: $6.35 million) on June 24.
Yandle is the prototype of a puck-moving defenseman, deployed exclusively in the offensive zone and on the power play to drive possession and boost scoring, but is not the type of player who will be used in the defensive zone or against top-six forwards.
Yandle's arrival addresses one problem, but may create another. With the departures of Campbell, Kulikov and Gudbranson, and unrestricted free agent Willie Mitchell, Alexander Petrovic was the only remaining defenseman with experience killing penalties or playing in other defensive-minded situations.
Rowe partially addressed that concern by signing unrestricted free agent defenseman Jason Demers to a five-year contract reportedly worth $22.5 million (AAV: $4.5 million) on July 2, but openings remain for players to contribute more defensively.

Nashville Predators

The Predators and Montreal Canadiens made the biggest splash of the summer on June 29, when Nashville traded defenseman Shea Weber to the Canadiens for defenseman P.K. Subban. The trade could be the key to unlocking the full potential of the Predators' young defense group, especially with the addition of veteran depth options Matthew Carle and Yannick Weber.
When Weber signed a 14-year, $110 million offer sheet with the Philadelphia Flyers on July 19, 2012, Predators GM David Poile had little recourse but to match the offer. Nashville had lost unrestricted free agent Ryan Suter to the Minnesota Wild two weeks earlier, and the remainder of the team's defense group was neither deep nor experienced.
Since then, the Predators have leaned heavily on Weber, deploying him for all the tough minutes against top opponents, and younger players such as Roman Josi, Ryan Ellis and Mattias Ekholm developed. Four seasons later, those young defenders no longer require the shelter Weber capably provided, and the time was right to trade his hefty contract.
Subban may not be Weber's equal when it comes to protecting a late lead, but Subban's incredible shot-based metrics are indicative of his elite possession-driving play. During his six full NHL seasons, Subban has increased Montreal's share of all shot-attempts from 48.1 to 52.0 percent when he's on the ice. That boost of 3.9 percent ranks ninth among defensemen to play at least 100 games during that span.