The biggest reason the Tampa Bay Lightning have morphed into a juggernaut this year is the front office’s success in remaking the blue line over the last couple of seasons. It started with the acquisition of Mikhail Sergachev. It continued with the trade for Ryan McDonagh last February. And it took another sudden leap forward when Erik Cernak joined the team early this season.

The Slovak defender came to the Lightning in exchange for Ben Bishop at the 2017 trade deadline. At the time, the trade was underwhelming. Bishop had been nominated for the Vezina Trophy as one of the best goaltenders in the league the previous season and rumors at the 2016 draft suggested he might be able to fetch a first-round pick.

At the time of the trade, the consensus on Cernak was that his development had stalled a little and he projected as a third pairing defender with an outside chance at being a number four. But from the moment he arrived in Tampa, he showed signs he could be more than that.

NHL teams don’t share much about their player development strategies but even from the outside, the difference between the Los Angeles Kings and the Lightning is obvious. The Kings, where Cernak was drafted, are a collection of aging talent at least partially because they’ve failed to successfully draft and develop through the declining years of their championship core.

Meanwhile, the Lightning have kept a steady flow of prospects from the draft, through junior hockey, into the AHL in Syracuse, and eventually to Tampa. The scouting staff hit another home run identifying Cernak as a trade target and we are now seeing the fruit of that work.

In his rookie season, Cernak has already emerged as one of the best defensive defenders in the NHL. His offense isn’t anything special yet. But it doesn’t have to be because he’s one of the rare players whose defense is a difference maker. And not in a Kris Russel media narrative way. In a real impact on the ice way.

That impact has been huge for the Bolts this year. Their constant search for a right-handed defender seems to be over. Cernak is the second pairing shutdown player they’ve been seeking. His success with McDonagh has stabilized the Lightning blue line allowing Dan Girardi, Anton Stralman, and Mikhail Sergachev to rotate between cushy spots of either playing with Victor Hedman or playing on the third pair against weaker competition.

To anyone watching the Lightning every night, Cernak’s importance to the team is obvious. But even the closest observer would likely underrate his impact his season. Because when we dig into the numbers, he looks like one of the very best defensive blue liners in the NHL this year.

All of the data that follows is via Evolving Hockey. A few weeks ago, we wrote a similar article about Anthony Cirelli’s defense. So if you read that, these visuals will be familiar. We’re going to use regularized adjusted plus minus (RAPM) at even strength and shorthanded to measure Cernak’s impact on the team’s expected goals against.

This first chart plots the two measures and Cernak is highlighted in blue. Negative numbers are good here because we’re talking about defense so the bottom-left quadrant is the best place to be. Immediately, the rookie defender stands out as one of the better defensive defenders in the league. And his impact is well-balanced between even strength and the penalty kill.

While the previous chart tells a good story, it doesn’t give us a single metric we can use measure players. The following chart combines the even strength and penalty kill impacts into total defensive impact.

Cernak ranks 8th here, which is impressive for a rookie who entered the league with little fanfair. We see lots of familiar names at the top of the list and an indication that the Capitals may have pulled off another trade deadline steal in acquiring Nick Jensen.

One other interesting thing to note is that lots of players on this list have strong even strength impacts but not so good penalty killing impacts. If we’re talking about the best defensive defenders in the NHL, we might want to limit only to players with positive impacts on the penalty kill. If we make that adjustment to the list, the following players remain.

Cernak has now bumped all the way up to third. Another Lightning defender makes an appearance here but probably not the one people would expect. Braydon Coburn continues to have an excellent season as he heads toward free agency hoping for one more contract. He’s been solid all year playing with a rotating cast of partners and even getting games off himself as part of the seven defender rotation the Lightning have been running since Cernak forced his way into the lineup.

Entering training camp, lots of people had their eyes on Cernak following a strong season in Syracuse. During camp, he looked like he might have secured a roster spot but the team’s depth forced him back to the AHL. That stint didn’t last long and he was the first player recalled after an early season injury on defense. And as soon as he got his chance, he made the most of it by being too good for the Lightning to send him back to the Crunch.

For a team stacked with offensive talent, Cernak is a perfect complimentary player. He gives the forwards the defensive support they need to play aggressively and makes a major impact without needing the puck on his stick to do so.

In other seasons, he would have a strong case for the Calder Trophy. But with Elias Petterson putting on a show in Vancouver this year, he’s unlikely to get serious consideration. Cernak is only 0.3 Wins About Replacement (WAR) behind Petterson but with the forward being much flashier and the more highly-touted prospect, he’ll run away with the award.

That’s probably a trend Cernak should get used to in his career. Players who make their primary impacts defensively never get the same recognition as players who drive offense. And even more frustratingly, the players who do get credit for good defensive play often aren’t even particularly good defensive players. Niklas Hjalmarsson has objectively been the best defensive defender in the NHL for years and hardly ever gets credit for it.

But that’s all probably secondary for Cernak. He’s playing a key role on a great team. He’s about to play the biggest minutes of his life in pursuit of a Stanley Cup facing other teams’ top lines. That’s a lot of pressure for a rookie. But if he handles it the same way he’s handled every other new challenge so far this season, he’ll confront it and conquer it. And if he does, he’ll start to get the attention he deserves