In conjunction with Stanley Kay's feature on Florida Panthers rookie sensation Aaron Ekblad, we present this ranking of hockey's most promising defensemen under the age of 23. To keep the focus on the game's best and brightest young prospects, we set a cut off at 200 pro games. The final order was determined with input from NHL scouts.

10. Morgan Rielly, Maple Leafs

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Not everyone is sold on Rielly's upside being this high, but two scouts made note of his ability to keep pushing his game forward during a season when so many of his teammates seem content to go through the motions.

“His perseverance this year has really impressed me,” one said. “He's had to step up with injuries to key players and really shown some moxie. He's really pushed himself to make the most of his opportunities.”

The 20-year-old has the kind of offensive instincts that should translate into a power play QB role and heavy minutes on Toronto's top pair. “He's a terrific skater, highly mobile, [and] has a real hunger for the puck,” another scout said. “He thinks the game like a forward, so he's always looking to push the puck up the ice.”

There's still a learning curve when it comes to his own end—Rielly's defensive positioning needs work—and he's about 15 pounds lighter than he should be. Eventually, though, he should put it all together to become a legitimate No. 1 defenseman.

9. Josh Morrissey, Jets

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The only player not yet in the NHL to make our list, Morrissey is a smooth-skating blueliner who plays the game with high-end hockey sense and eyes in the back of his head.

“He's a player who keys the transition,” a scout said of the 13th pick in the 2013 draft. “He releases pressure defensively by making that quick breakout pass. He's an offensive wizard. He'll be their power-play quarterback.”

Morrissey, 19, who was named to the All-Tournament team after playing a key role for the gold medal-winning Canadian side at the World Juniors, has arguably been the best defenseman in the WHL this season. It's a good bet that he makes the jump to the NHL for the 2015-16 campaign.

“He's so detail oriented, he's constantly working on his game,” the scout said. “He has that drive that you want to see. He's going to be an exceptional player.”

8. Adam Larsson, Devils

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Virtually an afterthought under former coach Pete DeBoer, Larsson has seen his career revived since Scott Stevens was brought back as a co-coach of the Devils. Under the close tutelage of the Hall of Famer, Larsson has rediscovered his confidence and started delivering on his immense promise.

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​“He's another kid who used to get buried [on the bench] if he made a mistake,” a scout said. “Now he's playing for people who trust him. He knows it's not the end of the world if he makes a mistake and so he feels free to try to make plays instead of playing it safe.”

That confidence has Larsson, 22, performing the way everyone expected when the Devils selected him with the fourth pick in the 2011 NHL draft. He's playing heavy minutes on New Jersey's top pair, where his skating, puck handling and ability to make quick, smart decisions are finally showing through.

“You can see that gleam in his eyes again,” another scout offered. “The passion, the swagger. He might need a couple more years like Victor Hedman did to really hit his stride, but his game's on track again. He's got all-world potential.”

7. Jacob Trouba, Jets

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Another player whose development has been slowed this season by injury, Trouba, 21, has all the athletic tools to become an elite top-unit defender. In 2013-14, he put together an outstanding rookie season, showcasing his two-way game by notching 29 points in just 65 games and averaging better than 22 minutes of ice time per game. He's a player who can handle duty on both special teams and can be used against the opposition's top stars.

“He's got so much going for him physically, you're just waiting to see him figure out the finer points of the game,” a scout said. “He can cover up the little mistakes with his skating and so there's a confidence level in his play that borders on cocky—in a good way. But he's really just scratching at his potential. He's already a big, strong kid, he's a beast, but he's going to get bigger and stronger. Winnipeg's got a good one there.”

6. Olli Maatta, Penguins

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There's no telling how many ladders were walked under, how many black cats' paths were crossed, that could have led to this nightmarish season for Maatta. The 20-year-old blueliner underwent surgery for the removal of a malignant tumor in his neck, suffered a case of the mumps and re-injured his surgically repaired shoulder, leading to another procedure—this one a season-ender.

So, yeah, it's probably a campaign he'd like to forget.

Fortunately, scouts have longer memories. And they haven't forgotten the impression that Maatta made as a rookie last season.

“He did pretty much everything for them. Stepped right onto the top pair, handled himself well against some high-end forwards, chipped in on both special teams. It caught a lot of people by surprise how comfortable he looked. He made it look easy.”

What that suggests is a player with elite potential.

“Sure, he's someone you can see being a fixture on that top unit, contributing at both ends of the ice, handling everything they ask him to do,” another scout offered. “If he can get past this [latest surgery], he's going a gamebreaker for them. He's going to be a top player in this league.”

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5. Ryan Murray, Blue Jackets

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Three years after being drafted second in the 2012 NHL draft, Murray, 21, remains a book scarcely opened. Injuries, including the high-ankle sprain that currently has him on the shelf, have limited the 21-year-old to barely 70 games over three seasons. But they haven't cooled the ardor of scouts who believe that he can become one of the very best in the game.

[daily_cut.NHL]“Yes, you worry about the injuries. Some guys, through no fault of their own, [injuries] just seem to follow them around,” a scout said. “You hope he's not one of those guys because all the tools are there to be a very special player."

That scout admired the quiet nature of Murray's game.

“He's not a flashy kid. He doesn't do anything that makes you jump out of your seat. He just keeps it simple, does all the little things well and keeps his mistakes to a minimum. Most kids, you have to worry about pairing them with someone who can cover for them. Murray's smart enough to take care of the other guys.”

That stability destines Murray for heavy minutes in a top pairing role once he puts on a bit of muscle. He'll never put up the big numbers, or handle power play duty the way a traditional No. 1 might, but his reliability, leadership and ability to stamp out brushfires make him a building block for the franchise.

4. Dougie Hamilton, Bruins

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The pressure of being the next great defenseman for a franchise that's dressed Eddie Shore, Bobby Orr, Brad Park, Ray Bourque and Zdeno Chara is probably too much to place on Hamilton. That said, there's every reason to believe that he can become an All-Star-caliber player for the Bruins.

In just his third NHL season, Hamilton, 21, has emerged as a workhorse in Boston. At 6' 5', 215 pounds, he's become stronger and smarter and his confidence has grown as he's gained more experience.

“Dougie can just take the puck and go” a scout said. “He's got that end-to-end ability, he's such a smooth skater. He can lead the rush, make a play and get back to cover up if the puck gets turned over.”

“Elite skill, elite vision, terrific offensive instincts,” said another. “In time, he can be that 25-minute defender that every team is looking for. He's a guy Team Canada will be looking at down the road.”

3. Seth Jones, Predators

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Jones is everything you could ask for in a cornerstone defenseman. Standing 6' 4" and headed toward 225-230 pounds, he's a smooth skating right-handed shooter who thinks the game at an elite level. Less than two years into his career, he's tracking to replace Shea Weber as Nashville's top defenseman.

Not that he's there yet. Jones, 20, has shown flashes of brilliance and even filled in on the top pairing alongside Weber for a stretch last season, but like most young defensemen he has some consistency issues to work through. That's been more apparent lately as he's had to assume a larger role in the wake of key injuries on Nashville's blueline.

That said, scouts think he's in the perfect situation to realize his full potential.

“Playing under Peter Laviolette, that's ideal for him,” one scout said. “He’s got the legs and the smarts to lead the rush and become a point producer, and [Laviolette's] system is made for guys like him. He can make mistakes and not have to worry about being [benched]. He can get back out there and figure it out.”

In time he'll become that top-pairing defender who supports, and then takes over for, Weber. “He's got the potential to be a Norris-caliber player,” another scout said. “He's a guy you win Cups with.”

2. Aaron Ekblad, Panthers

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“You can't overstate what he's accomplished as an 19-year-old player,” a scout gushed of Ekblad, the top pick in the 2014 draft. “He plays the hardest position [to learn] in the best league in the world and makes it all look effortless. He already looks [and plays] like a 28-year-old. Five years [from now]? He might be the best in the game. He's that good.”

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Ekblad's transition from junior hockey to the NHL hasn't been seamless, but it's been pretty close. Blessed with enviable size and maturity, he's handled a heavy workload that usually tops 22 minutes per night against the opposition's top lines.

What's really impressed scouts is how quickly he's adapted to the pace of the game. “His reads, his hockey sense, it's all off the charts,” our scout said. “The game is slow for him. He knows what's coming and how best to react to it. That's why he makes so few big mistakes.”

It's also why he's tied for fifth in rookie scoring with nine goals and 32 points, trailing forwards Johnny Gaudreau, Filip Forsberg, Mark Stone and Mike Hoffman, and why he's the favorite for the Calder Trophy.

“He has the potential to dominate the game at both ends in a way we haven't really seen since Ray Bourque,” the scout said.

1. John Klingberg, Stars

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It's easy to find comparables for the 22-year-old rookie. Because he's Swedish, some look to Erik Karlsson. Because he plays for the Stars, others point to Sergei Zubov. There are certainly echoes of both players in his game, but Klingberg is his own man, a thoroughly modern defenseman who makes things happen with his hands and feet and his vision instead of brute strength.

“He's got ice in his veins. There's no panic in his game,” one scout told SI.com. “His ability to maintain his composure under intense pressure is what makes him so effective.”

A late arrival this season—he made his debut in early November—Klingberg has quickly developed into a top-pairing defender for the Stars. A smooth skater, he uses his speed to drive the team in transition and zoom back to handle defensive zone issues.

But his greatest strength is his ability to get the puck to the net. "It's a rare talent these days because everyone is so good at getting sticks and bodies into the shooting lanes," said a scout. "Klingberg has great mobility and vision—he knows when and where to release his shot and he gets it to the net in a hurry."

His top ranking on this list will surprise some, but one scout we spoke to was quick to back up the selection. "He's the type of player every team wants these days. He defends by making plays. He makes everybody around him better. And he's always trying to make himself better. He could be a Norris contender in a few years."