His relentless, havoc-causing playing style quickly earned him the nickname Stormy.
"He used to skate the fastest from one end of the rink to the other, causing a storm," said Walker's mother, Ceri. "The name has stuck with him since then."
Still playing with the same seemingly endless energy, Walker is eager to make a name for himself with the Washington Capitals as the first Australian to play in the NHL. The 23-year-old left wing is scheduled to make his debut Saturday in the home opener against the Montreal Canadiens at Capital One Arena (7 p.m. ET; CITY, TVA Sports, NBCSWA, NHL.TV).
Walker, who was born in Cardiff, Wales, before moving with his family to Sydney when he was 2, understands that his first NHL game will be significant not only for him and his family but also for Australia.
"I'd be pretty proud to represent not only myself, but the country and Australian hockey as well," Walker said this week. "It would be something to get Aussie hockey on the map."
Hockey ranks well behind soccer, rugby and Australian-rules football in popularity in his country, which has a population of more than 24 million, but Walker has become the sport's key figure there.
A Facebook page called "Latest on Stormy" has more than 1,000 members who kept tabs on Walker throughout training camp.
Video: WSH@NJD: Walker buries rebound to tally SHG
"It would be the biggest thing to happen to Australian hockey ever," said Stephen White, a play-by-play announcer for Australia Ice Hockey League games on Fox Sports Australia. "Australia is known for its sporting prowess, considering we're a comparatively smaller country in terms of the American market. We've got great representation in the NFL, the NBA and in Major League Baseball. The NHL has been like the last frontier for us and it's the hardest one to make from Australia and what he's done, in my opinion, it's the most remarkable and the hardest to achieve.
"It would just be massive for the sport down here. The Capitals have just got 24 million new fans."
In June 2016, Wayne Gretzky, the NHL's all-time leading scorer, visited Australia for the Wayne Gretzky Ice Hockey Classic, a series of exhibition games between teams from the United States and Canada. While in Sydney, Gretzky invited Walker and his fiancee, Tayla, to have dinner with him and his family.
"It was really special," Walker said. "We didn't really talk about hockey. It was nice to just kind of meet him and be around him without having the hockey talks."
Gretzky is credited with inspiring a wave of hockey players from California during his eight seasons with the Los Angeles Kings after they acquired him from the Edmonton Oilers in 1988. Though Walker's game is more about energy and physicality than scoring, he could have a similar impact on a smaller scale in Australia.
According to Ice Hockey Australia, there are 4,800 registered hockey players, including men, women and juniors, in the country. That number is expected to grow to more than 6,000 after summer-season registration, and there are wait lists for junior teams.
Ice time is precious with 20 rinks in the country, but AIHL assistant commissioner Lisa Martens said $23 million (about $18 million U.S.) has been committed nationwide toward new ice-rink construction and upgrading existing rinks.
Interest in the eight-team AIHL is also growing. The 2017 AIHL Final between the Melbourne Ice and CBR Brave on Sept. 3 drew more than 14,000 viewers on livestreaming around the world, an increase of 6,000 unique viewers from the league's previous high for the final.
Having an Australian playing in the NHL would bring even more attention to the sport.
"It would probably the greatest thing to happen to Australian hockey since the 'Mighty Ducks' movie," said Scott Stephenson, an AIHL player with the Sydney Ice Dogs who coached Walker at the peewee level and later played with him on the Australian national team. "But I think the most important thing is it just shows his perseverance and hard work and it can really show anyone that there is light at the end of the tunnel and the reward."
Walker was one of a generation of Australian players drawn to hockey by watching "The Mighty Ducks," which was released in 1992, and its two sequels. Walker was also influenced by watching his older brother, Ryan, play.
When Walker began dreaming of playing in the NHL, he realized he wouldn't get there if he stayed in Australia. So he left behind his family and moved to Ostrava, Czech Republic.
"I wanted to be on the ice all the time when I was younger and I just couldn't do it back home," he said. "There weren't the facilities and the ice time available for me to do that."
Walker spent six seasons honing his game in the Czech Republic, including the final two with HC Vitkovice in the top Czech professional league. In January 2013, he came to North America to play for Youngstown of the United States Hockey League.
Though Walker was passed over in the NHL Draft in 2012 and 2013, the Capitals invited him to their development camp each year. That led to an American Hockey League contract with the Capitals' affiliate in Hershey in 2013-14, and Washington selected him in the third round (No. 89) of the 2014 NHL Draft, making him the first Australian to be drafted.
There was little hope of a call-up when the Capitals were winning the Presidents' Trophy the past two seasons with a loaded lineup. But after an offseason of roster turnover created some openings, Walker made the team with a strong training camp.
"He's still extremely young and he's ready," Capitals goalie Braden Holtby said. "You can tell on the ice he's involved in every shift. He's one of those players that can add a lot to our roster."
Ceri Walker said: "Nathan has made a lot of sacrifices since a very young age, being away from home since the age of 13, living for years in a country whose first language was not English, living with a family that he did not know, spending endless Christmases on his own, missing out on all family and mates' celebrations. If he steps out onto the ice on opening night, then it would have been all worth it, and we can all scream, 'He did it!'"
Ceri and Wayne Walker, Nathan's father, will be there Saturday for the big moment. They had waited in Australia with their flight plans on hold, hoping to hear when Nathan would play.
"No way do I want to watch it online," Ceri Walker said.