The 18-year-old had no choice but to grow up fast.
At 13, Hanifin was in the eighth grade and playing varsity hockey at St. Sebastian's School in Needham, Massachusetts, when his father, Bob, was diagnosed with colon and kidney cancer. During his dad's yearlong chemotherapy treatment, Hanifin became the man of the house, helping his mom and two younger siblings.
"Any hockey player can say their dad had a big impact on their life, taking them to the rink every day," Hanifin said. "When he was sick, it was the first time I have had to deal with adversity. It may not have been hockey, but it was some sort of adversity. It made me grow a lot as a person. Just going through that experience with my dad, I matured a lot as a person, and that ultimately helped me as a player."
At June's draft, Hanifin was in the stands at BB&T Center in Sunrise, Florida, when his name was called as the fifth overall selection. His parents, younger brother and sister were with him.
"It was awesome. It was a dream come true," Hanifin said. "It was such a surreal experience. You don't really get it until you're there on that day and you're sitting there so nervous with your family. Luckily for me, I was drafted by the Hurricanes, and to be able to go through that with my family was one of the best feelings of my life."
No. 1 pick McDavid (Edmonton Oilers) and No. 2 pick Eichel (Buffalo Sabres) were locks to make their NHL rosters. But the third and fourth picks --Dylan Strome (Arizona Coyotes) and Mitchell Marner (Toronto Maple Leafs) -- returned to their respective junior teams.
Hanifin signed a three-year, entry-level deal in July after impressing the organization's executive vice president and general manager Ron Francis, who said at the time that Hanifin fits the mold for the type of player and person the team wants to wear a Hurricanes uniform.
"My ultimate goal was to get to this level, and now that I'm here, I'm not going anywhere else now," Hanifin said. "I can focus on what I need to do to keep getting better. I want to take my game to the next level in the next few years, so I want to be one of the best defensemen in the NHL."
At 6-foot-3 and 206 pounds, Hanifin played his first preseason NHL game, against the Pittsburgh Penguins, on Sept. 22. On his first shift, he was a bit aggressive and stepped up to hit the Penguins' Phil Kessel, who quickly made a pass and sprung Sidney Crosby on a breakaway.
It was Hanifin's "welcome to the NHL" moment.
After playing only one season of collegiate hockey at Boston College, Hanifin hasn't had an easy transition to the NHL. He has played 13 regular-season games and been a healthy scratch three times.
"It's been hard," he said. "It's been a big adjustment this year. Every day you're learning something new. Coming into camp until now, I think I'm a better player, just with the little things, the little details of the game."
In the past, Hanifin was the best on the ice simply for his skating ability, size and hockey sense. It's different in the NHL.
"Everybody has that," he said.
During a recent game against the New York Rangers, Hanifin sat on press level and watched his team lose 3-0 at Madison Square Garden. He's a competitive kid and wants to play every game, but he also understands it's part of his development.
"Sitting out games obviously hurts because you want to go out there and play, but at the same time you have to be positive about it and learn and take away what you can from watching the game and being around pro athletes every day," Hanifin said.
Developing his pro game now, and honing his skills at this age should prepare him for a successful career. One of his goals is to be settled in by his early 20s.
"I felt that, even though I would be challenged, I could come in at this age and I could play and I could learn," he said. "I don't think I would hurt myself playing at this level, at this age. Hopefully, if I get a few years experience, I'll still be young but I'll be able to take my game to the next level when I'm 22 or 23.
"I'm just focused on what I need to do because it's such a hard level. Everyone's different, and guys come into the league at 18 and they'll be ridiculous like Connor and Jack, but for me it's hard being an 18-year-old defenseman. It's pretty tough."
Think about this: Only three years ago, Hanifin was playing high school hockey at St. Sebastian's School. He then played for the U.S. national team development program under-17 team and, at 17, was the youngest player ever to play for Boston College.
Hanifin's road to the NHL has been quick, but Hurricanes coach Bill Peters has been impressed with the rookie's development.
"It's been good," Peters said. "It's a big step from where he was three years ago. We were talking about it at [the Hall of Fame] ceremony [Monday night] that three years ago he was playing high school hockey, so it's a big step over a 36-month period, and he's handled it well."
Despite Hanifin's age and inexperience, many believe he has the staying power to play in the NHL and develop into a top blueliner.
"For sure he does, but we have to do the right thing over the course of this year and over the course of the next two years in his development," Peters said.
"A very poised kid," said one Western Conference scout. "He's a great skater with good hockey sense. In time, he'll add some offense and be a good two-way defenseman. He can move the puck, defends well and can play in all situations. He does not get rattled and is very poised for his age."
The past few summers, Hanifin has been working out with many local NHLers, including Keith Yandle and Kevin Hayes of the New York Rangers, Jimmy Hayes of the Boston Bruins, and Brian Boyle of the Tampa Bay Lightning. Yandle and Kevin Hayes were disappointed when Hanifin was a healthy scratch Tuesday.
"They're probably doing the right thing with him, letting him see the game from up top and play games when he needs to," Yandle said. "He's a young 18-year-old kid, and the way he handles himself on and off the ice -- and I saw a lot of it last summer working out with him -- to see a young guy like that is impressive."
Jimmy Hayes was always impressed with Hanifin's willingness to put in the extra work in the offseason.
"He has a commitment to everything," Jimmy Hayes said. "He's a really strong kid for 18 years old. He's already built like a 25-year-old. He already has the God-given talent, but the way he skates, and the way he can shoot the puck, and the way he can skate through the middle at such a young age with confidence, it's going to be a pretty easy transition for him into the NHL."
Life prepared Hanifin for his professional career, and he's off to a solid start.