It was early July of 2013 and the Calgary Flames made one of those minor transactions that barely registered on the NHL radar screen – Kris Russell coming over from the St. Louis Blues for a fifth-round pick. That same day, the Ottawa Senators made a far bigger splash, acquiring Bobby Ryan in a blockbuster deal with the Anaheim Ducks. The day before, the Boston Bruins rocked the league by trading Tyler Seguin to the Dallas Stars.

And yet, here is Russell, almost two years later, the undersized (5 feet 10, 172 pounds) defenceman originally from Caroline, Alta., having emerged into one of the key performers in the Flames' playoff push. Even before team captain Mark Giordano was lost because of season-ending biceps surgery, Russell had been playing a top-four role, his chemistry with Dennis Wideman an unmistakable part of what made the team click. In Giordano's absence, both Wideman and Russell have been playing upward of 27 minutes a night, yeoman's duty for a defensive pair that casual hockey fans are barely aware of.

Russell, now 27, was an offensive defenceman in junior and put up almost a point-a-game in his final three seasons in Medicine Hat. In his draft year, 2004-05, he scored 26 goals in 72 games, but slipped to 67th overall, largely because of his size.

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The only statistical category he dominates any more is shot-blocking. On Thursday night, in the Flames' come-from-behind win over the Boston Bruins, Russell blocked 15 shots, the highest single-game total in NHL history. The previous mark was 12, most recently set in 2009 by Colorado's Brett Clark. Even before his record-setting performance, Russell was already the runaway leader in the shots-blocked category, with 218, ahead of Nashville's Roman Josi (175) and Washington's John Carlson (159).

It primarily takes two qualities to be an expert shot-blocker – courage and technique.

Courage generally comes from within and, according to coach Bob Hartley, is a quality Russell possesses in abundance.

"If it would go by the size of his heart, Kris Russell would be the biggest defenceman in the league," Hartley said. "He's an unbelievable big part of our hockey club, on the ice and off the ice. We didn't give him an 'A' without a reason. This guy does lots that you don't see."

Technique, Russell says, is something he learned in his early years with the Columbus Blue Jackets, under the tutelage of former NHL defenceman Gord Murphy, who was an assistant coach with the Blue Jackets.

"It's something I've gradually gotten better at," Russell explained. "Being how small I was, coming into the league, [Murphy] stressed how important it was to have a good stick; how positioning was the key for me because I'm not going to be able to overpower guys, so I can't lose body position. I've had a lot of good coaches and played with a lot of good veteran players, like Adam Foote, my first couple of years in Columbus. I could listen to what he had to say and get knowledge that way."

Russell was drafted originally by Columbus and then was traded to St. Louis for defenceman Nikita Nikitin. He played parts of two seasons with the Blues, but when they acquired both Jay Bouwmeester from Calgary and Jordan Leopold for second- and fifth-round picks at the 2013 trading deadline, he got caught in a numbers squeeze. The Flames, seeking a depth defenceman, were the unexpected beneficiaries of that surplus.

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"It was a good organization to come to because of the coaching staff," Russell said. "It doesn't matter where you come from or how much money you make, they're playing the guys that are going. That's all you can ask for as a player."

Five-on-five, the chemistry between Russell and Wideman just works and Hartley, who tends to mix and match his forward-line combinations, has left his defensive pairings alone virtually all year.

"I think we read off each really well and our communication's very good," Russell said. "It helps that we're buddies off the ice. Having a good relationship, on and off the ice, just helps. Reading off Wides [Wideman], he's got a big shot, so when he's jumping up on the rush, if something happens, if the puck jumps or a guy falls and the play's coming back, I've just got to make sure I'm there – and vice versa, too. If I have the opportunity to go, he's done a good job of backing me up."

The most telling example of how much the Flames valued Russell's contributions came just before the season began, when they named him an assistant captain. With Giordano injured and Curtis Glencross, the other assistant, traded away last Sunday, Russell is now the de facto captain.

"Russ is a quiet leader; he does it on the ice and those are the best kinds of leaders," assessed Giordano, who added: "Oh man, he's so underrated. For us to get him a few years back, I knew he was a very good player, but just his patience with the puck and his ability to make plays is obviously No. 1 in his game."

Russell acknowledged he was "a little surprised" when management gave him a letter at the start of the season, noting: "I wore one during exhibition, but in exhibition, you don't have a lot of vets in, so I didn't read much into it at all and didn't expect to come in and get a letter.

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"But at the same time, we have a great group of leaders – [Matt] Stajan, Wides, [Jiri] Hudler – who've got a lot of experience and are important voices in our dressing room. I think that's why our team has been successful. It's not just Gio taking the whole weight on his shoulders; it's other guys stepping up and trying to help as much as they can, too."

Something that'll need to continue more than ever for the Flames to stay in the playoff chase.