After being with the team for a month following Dennis Seidenberg's season-ending injury, he hadn't been able to reflect right away on the changes in his career, going from making his debut with Boston in November, to becoming a fixture on the blueline for the rest of the season.
"It's been a good journey, but it's not done yet," the 26-year-old had said.
Seven months later, Miller has 58 NHL regular season and playoff games with Boston next to his name, and he's putting in all of the offseason work to make sure that his progress doesn't stop there.
A native of Santa Clarita, California, in greater Los Angeles, Miller heads home every summer to train. It's there to he first started dreaming of playing in the NHL, even if it wasn't the norm for most kids his age, being in sunny, warm SoCal.
In LA now, he's surrounded by friends he grew up playing with (and are still working towards their dream of playing in the NHL) and other local players.
When our BostonBruins.com crew caught up with him Wednesday in Los Angeles for a #BearTracks summer road trip, he had the chance to look back at his year and being able to share the experiences with his friends back in Cali.
"Oh, it's been great," Miller smiled. "It's obviously some time now after the season to reflect on things and it's a good feeling and it's good to be home."
"But we're already looking forward to next year."
The seasons didn't end the way it was supposed to be for the Black and Gold, they know that. But as the months go by, and this past May gets farther in the rear view, Miller and his teammates are focused on what lies ahead.
And the summer months are a time to get ahead.
"I mean, you want to use it to your advantage," said Miller. "I don't like to take too much time off, and you definitely use it to make sure you're in the right mindset for next season."
For the 6'2' roughly 210-pound blueliner, that means building and maintaining his strength - his biggest asset on the ice - while also continuing to develop other aspects of his game.
The work is never done, especially for Miller, who has only started his NHL journey after a fairly long road to get there.
He moved away from California at age 16 to attend Berkshire School in Western Massachusetts, following that up with a four-year college career at the University of Vermont and two full years pro with the Providence Bruins before getting a chance to show his hand at the NHL level, making his debut on November 21, 2013.
When we first arrived to Los Angeles to meet up with 'Millsy,' he was in full equipment and ready to head out to the ice at the Toyota Sports Center (the LA Kings' practice facility) for about an hour-long, high-tempo skate that includes a few of those buddies he grew up with in California.
"I don't like to let myself get off the ice for too long, so it's kind of been an ongoing process," he said.
With drills and countless shots from inside the blueline, you can tell that Miller has a purpose to everything he does - even if it is an afternoon session in the middle of a Los Angeles summer.
As always, the blueliner is continuously looking to improve his game.
"Just a number of things, being able to make plays and work on my hands, and also working on my shot, seeing what else I can bring to the team," said Miller.
He had 103 hits and 85 blocked shots suiting up in 47 games for the Bruins during the 2013-14 season, along with his first four NHL fights.
Like Dennis Seidenberg, he's heavy on his stick and has a strong, low center of gravity that helps him knock down opponents without even using much force. His most emphatic hit came on LA Kings' captain Dustin Brown at TD Garden, when he up-ended him into the boards, causing 'And down goes Brown!' to be the play-by-play.
Dialed in, Miller hadn't heard during the game how the crowd had erupted.
Across the country, Bruins President Cam Neely and General Manager Peter Chiarelli, along with the management team and scouting staff was watching that game from their mid-season scouting meetings in Las Vegas.
With a contract extension already in-progress for Miller, they signed him to his new deal the next day.
Seeing the defenseman in California, already back on the ice, and with a clear view of what he's accomplished and wants to accomplish, it's easy to notice the attitude that has gotten him this far.
Away from the serious grind of the NHL regular season, and away from any sort of spotlight, it's the work in the offseason that puts players ahead of the game when it comes time for training camp.
Miller knows that, and it's why he's even adopted a new part of his summer routine, twice a week taking part in ELDOA, a class that helps keep his spine healthy, realign the body, eliminate back pain, work on his balance and core strength, and open of the tightness in his hips and upper back - where the NHL wear and tear really makes its presence felt.
Nashville Predators forward Eric Nystrom got Miller into it, out in LA.
Watching the defenseman on the ice is one thing - it's effortless for him, especially with his pure strength.
Watching the defensemen and the rest of his class on Wednesday night in Santa Monica, led by therapist and personal trainer Deane Birkett, hold difficult yoga-like poses, purse their lips, and sweat out buckets was definitely not what we were expecting.
"This is way harder for me," laughed Miller, who graciously let the cameras document what is not an easy workout for him. "This is way harder for me than weight training or anything like that. It's a lot of holding your body in different situations and if you're just looking at it, it doesn't look as hard but then you go and do it, and it's definitely challenging."
"I think it's because my hips are so tight," he laughed, while explaining the difficult poses.
"That's something I need to work on, and something that I'm trying to get better at, so, anything that can help."
There's always something to work on, right?
"Always something to work on," he said.
The trainer, Deane Birkett, hasn't known Miller for a long time, but he saw something in him right away.
"He works hard," was Birkett's immediate response when I asked what he's learned about the defenseman nice he's known him.
"And the reason why is, he's got a goal. And he realizes, he's smart enough, he's an intelligent athlete and he realizes that if he wants a long-term career to be able to sustain the knocks, open up the joints so that when he does sustain the knocks, the joints can handle it."
Miller's game revolves around his physicality and tough nature.
He'll keep working on that, along with trying to improve his offensive game, and his shot, which he hopes to have more lethal and more accurate come September.
So, should we be expecting a Johnny Rocket?
"A Johnny B. Rocket. I've been texting him for advice," he laughed.
With a full day of skating and working out, Miller was ready for some relaxing time.
'You guys don't really take much time off, do you?'
Even if he is in sunny Southern California.