The 27-year-old, who is now co-captain alongside Alex Waller, enjoyed a proud moment last Sunday as he reached his latest milestone after leading the team out against Bristol.
The result wasn't the one he wanted as Saints suffered an agonising 20-14 defeat, but Harrison had once again shown his worth.
He produced yet another all-action display, delivering a moment of first-half magic as he helped to set up a score for Harry Mallinder.
In those few seconds, there was an exhibition of all that is good about Harrison as he demostrated his incredible desire to hold players off before showing the skill to time and place the offload perfectly.
He has become so vital to this Saints team, completely bossing the No.8 shirt this season to leave Saints wondering just where they would be without him.
For his part, Harrison is loving every second of life at Saints, who he first joined as a member of the Senior Academy in late 2011.
And he was so proud to reach 150 appearances last weekend.
"It was a wicked moment and it's one every player aspires to because you always want to hit milestones for your club, especially a club that you love and enjoy playing for," Harrison said.
"It was honestly one of the best moments in my playing career."
Opotiki-born Harrison arrived at Saints after being scouted by Dylan Hartley during the 2011 World Cup in New Zealand.
"My body definitely tells me it was a long time ago, with aching and whatever, but it's been an awesome journey to where I am now," Harrison said, smiling broadly. "It's one that I wouldn't change.
"I've really enjoyed every game I've played for the Saints - win or lose, it's always an honour pulling on the shirt and running out with your boys.
"I remember my first Prem game was Wasps at home (in 2012).
"I remember getting a ball just inside the 22 and seeing the try line. I was like 'come on, it would be wicked to score' but it didn't happen.
"When I first arrived at the club I met Dylan here and Paul Doran-Jones.
"I remember heaps from when I first came here, just walking into the stadium because I'd never seen a stadium in England before.
"I'd never really followed English rugby and it was a bit of a shock to see how well put together everything was.
"The first game I came and watched on the weekend I got here, I got that buzz from the fans and everything around here.
"There's definitely something special here."
So how much has Harrison changed during the past nine years?
"I can string a sentence together now!" he said.
"I'm not so crazy in the way I go about things on the field.
"It was a massive work-on for me, especially when Westy (Dorian West) and Jim (Mallinder) were here. They tried to keep my aggression the same but take the mindless things out of my game.
"My haircut has changed - it's on the path back but I don't think we'll ever see the dreads again which is a bit of a shame."
So impressive has Harrison been in recent years, he was handed the chance to be a co-captain by boss Chris Boyd last summer.
"I love the responsibility of it," Harrison said.
"I love being something of a role model to the younger guys.
"I enjoy playing here and whatever comes on top of that is a bonus.
"Being a co-captain is something I'm really enjoying and I hope to keep doing the club and the boys proud."
The fact Harrison has not made it into England's Six Nations squad may come as something of a shock for those who watch him week in, week out.
But there is no doubt that country's loss is club's gain as Saints really need Harrison right now, especially with the pack severely depleted by absences.
Saints have lost their past two games, both at home, to London Irish and Bristol.
It has been a hugely frustrating spell for the Gallagher Premiership's second-placed side.
And Harrison said: "It's not even about the teams we're playing, it's about our position in the league.
"We're aspiring to get a home semi-final and those two games are crucial and the points will definitely be missed come the end of the season.
"We're back in the pack fighting for our position whereas if we'd won those two games, even taken four points, it would have been a nice little buffer.
"We could potentially have been sitting top and it's a real shame.
"For the players, it's a bit gutting to let games like that slip, especially when we were in control during the first half.
"We were forcing them to make errors they wouldn't really make, we put pressure on them and we should have come away with more points in the first half of both games.
"But there are no excuses for the second half of the games because we either stopped playing or let them back into the game from stupid individual errors.
"It's 10 minutes of loss of concentration, your back is against the wall and that opportunity is gone."
There would be no better way to bounce back than by beating Exeter Chiefs and Saracens during the next two weeks.
But trips to Sandy Park have not been enjoyable for Saints in recent times as they have lost on their past eight visits to Exeter, failing to win there since February 2014.
"It would have been nice to have the points on the table in the past two games and not have to go away to the top team and get the result," Harrison said.
"We will go out there and give it everything but it is disappointing not to have to results in the past two games.
"Exeter is a tough place to go and play because they are a well-drilled team.
"They don't play much with the ball in their own half. They wait for you to make a mistake and they capitalise on it.
"They've got a very strong forward pack, they love to get scrum and maul and when they get into your 22 and to five metres out, they grind you down with phase after phase of pick and go.
"But like every team, they have got their weaknesses and we'll look to exploit them."