On that day - June 24, 2011 - he was a 6-foot-4, 193-pound defenseman, who had spent two seasons playing for the Niagara IceDogs in the Ontario Hockey League.
When he arrived to the 2011 NHL Entry Draft in St. Paul, Minnesota, he didn't yet know where his path to the NHL would officially begin. When the ninth pick came around, he finally knew that path would be in Black & Gold.
Now, in his second NHL season with the Bruins, Hamilton found himself back at the Xcel Energy Center on the morning of March 8, 2014, for the first time since that day.
In St. Paul to face the Minnesota Wild amidst the team's final push to the postseason, Hamilton went through his gameday routine, hitting the ice for pregame skate with his teammates and then taking a seat in his stall in the visiting team locker room.
"It’s pretty cool," said Hamilton, taking a look around the room. "I think I'm just trying to piece it together, it’s a little bit different with ice out there and everything, but I remember taking some pictures in this room."
"It’s just, a cool memory to be back here."
Could he believe it had already been three years?
"No," he quickly answered. "I said that to my mom yesterday. I was like, it feels like yesterday and it’s pretty crazy how fast it’s gone…you can’t really complain with that, though."
Within those three years, Hamilton has quickly grown, on a number of different levels.
Physically, he's gained an inch and 20 pounds. Mentally, he's learned how to handle the schedule, handle himself as a pro, and handle any nights out of the lineup, whether due to injury or as a healthy scratch.
The defenseman played his first NHL game on January 19, 2013, after the lockout came to an end and his services were called upon from Niagara. He played his 100th NHL game on April 2 in Detroit. Much growth has happened during that time, and especially since 2011.
What does the 20-year-old see as the biggest difference?
"The black eye," he quipped, in reference to the black and purple ring that had formed around his left eye since taking a stick up high about a week prior in Toronto. The blue thread of the stitches was still there, too, sewing up the gash.
"I think I’ve honestly changed a lot, matured a lot, and hockey-wise, I think I’ve gotten a lot better as a player," reflected Hamilton, switching to a more serious tone. "I just trying to keep improving on everything as a person, and as a player, and I think I’m pretty happy with the changes I’ve made in three years."
When the Bruins drafted Hamilton, they knew they were getting a tremendous skater, with offensive instincts, and strong range as a player. He had a good, physical side to his game by his final OHL season, after he grew more into his frame and learned how to test his strength and size.
"He's big, and he continues to grow," General Manager Peter Chiarelli had said in 2011. "Without placing a burden on him, he plays a little like Rob Blake. Good skater, good shot, can make plays, handle the puck."
Since Day 1, the poise has been there for Hamilton. He uses his hockey sense to his advantage, and in turn, that also helps his usual partner on defense, the 6-foot-9 Zdeno Chara.
"Honestly, I’m honored to be playing with him and I think it’s just more comfortable with him on the ice," said Hamilton. "I think I know more where he is now, whereas last year when I was playing with him or at the start of the year this year, I think it’s a little bit different because you don’t really know. So, just more chemistry now."
"[Now,] I’m used to playing against another team’s top line, so I think it’s just, for me, trying to do my best for him and be accountable."
Hamilton may be 17 years younger than Chara, but The Captain has always taken to the blueliner, whom he made sure not to tab a "rookie" when he first joined the team in January 2013.
Sitting near each other in the locker room, and paired together off and on amidst the 2012-13 regular season, that bond grew.
But for Hamilton, who had been playing nonstop hockey for a year (with international competitions and his junior season), and had no NHL playoff experience, the then 19-year-old was a healthy scratch for six games towards the end of the season.
Hamilton suited up in just seven postseason games, including Games 5, 6 and 7 against Toronto Maple Leafs, and the first four games against the New York Rangers.
"He’s got experience now, he’s got another year under his belt but even so, I think in the last month or so, I think his game’s really picked up," Julien said early this April. "His confidence is a little bit more assertive which is what we want him to be and that’s definitely caused by some confidence, and playing with Zee helps too."
"And when I say playing with Zee, he’s got the confidence and he knows he’s got a big time partner there on defense so he can play his game, but at the same time, I think he’s very capable of helping Zee as much as he is helping him."
"He’s got a great vision, he’s a good skater, so as a partner to Zdeno right now, he’s the young legs right there and there’s no doubt he can certainly help this guy."
Hamilton would probably never admit he's helping his mentor, because he doesn't necessarily see it that way. He just continues to learn to play to his strengths, by playing next to a defenseman who has mastered his own.
"Obviously no one’s Zee, but I definitely can learn from him - how he plays and take things from his game and I think for me, as a bigger guy who can skate, just kind of using that to my advantage," said Hamilton. "So you’re always working on different things and lately I’ve been trying to be more physical. Hopefully I can continue doing that and keep working on that."
Back in March, when the Bruins powered out a 5-1 win over Carolina, Hamilton sized up Jeff Skinner entering the Bruins' zone. The Hurricane cut to the middle with his head looking down at the puck, and Hamilton launched him with a pounding open-ice hit.
Throwing a hit like that certainly drew attention for the young blueliner, and if he finds an opposing forward with his head down again, you'll see the same result, whether it's him or another Bruin throwing the heavy hit.
But for Hamilton, his focus on "physicality" isn't about those hits.
"I’m working on my game, trying to be physical, but I’m not sure there’s as many big, open-ice hits any more. Those are pretty rare, so it’s more just battling," said Hamilton.
For him, it's more about the upped compete level in one-on-one battling and using his body to his advantage.
"I think last year I was kind of in and out at this time and right now, I’m trying to earn my spot in the playoffs and be physical and trustworthy - and make them want to play me in the playoffs," he said. "So I’m just trying to do my best to be consistent and do that every game and hopefully, earn my spot in the playoffs."
On many teams, Hamilton would have already been forced into that type of heavily relied-upon role.
"He came in here as a 19-year-old. A 19-year-old that’s on a team that’s rebuilding is going to play a ton; a 19-year-old that’s on an established team doesn’t get the same luxury," Julien has said, of the defenseman's situation, one that is much different than most early first round picks. "But he gets the luxury of developing in a winning environment and finding out quickly what it takes to win, so he’s in a good situation."
"I think he trusts us, I think we know what we’ve got, he knows that we know that as well, and it’s just a matter of being patient."
"You can see that effort in him, and it’s trust, it’s respect and that has to happen both ways."
Hamilton is staying patient off the ice, but he has gotten more assertive with his play on the ice.
His first shiner may have come from a high stick, but it's a look Hamilton wouldn't mind having in the postseason, if it comes from battling and the intensity of having his way along the boards and in the corners.
"Not really a 'whatever it takes' moment but moving into the playoffs, I'd be willing to get another one, I guess you could say that," said the blueliner.
"There are a lot of guys on our team that have scars and bruises all the time; it's the Bruin look."
It's also a look indicative of the Stanley Cup Playoffs, and Hamilton is pushing to play a strong role in them this time around.