BRETT Ratten was driving into Princes Park in the sleepy hours of a summer morning, expecting as ever to be the earliest player to arrive for Carlton's first pre-season training session of the 2003 campaign.

A Blues stalwart and a premiership player with the club, Ratten was preparing for what would prove to be his final season as a player. Across each of his 14 years in the Navy Blue, he had been renowned for his work ethic, his dedication, and his first-one-in, last-one-out mentality.

Except on this morning, he wasn't the first one in. As the Carlton captain strolled towards the Princes Park entry, a scrawny teenager was fumbling over the entry code in front of him, trying unsuccessfully to gain access into the club's headquarters.

Kade Simpson had just been recruited to the Blues only a few weeks prior, a small, skinny wingman weighing barely 70kgs out of Eastern Ranges. He was there early to make a good impression on his new teammates.

But there was making a good impression, then there was arriving for the first training session of the summer three full hours before the playing group had been instructed to.

"I remember when he first got there … he was a tiny little fella and he didn't grow too much, but gee he had a big heart," Ratten tells AFL.com.au.

"Really, he never put that much size on. He just found a way to make it all work. He was such a brave player for his frame given what he did. To be so resilient, to play 300-odd games, it's amazing.

"He hasn't just impressed me over these 18 years, he's impressed the footy world. That's something he and his mum and dad – Gail and Terry – can be extremely proud of. He's done so much in the footy space and he's got so much respect from so many people. He should be so proud of what he's done.

"To be a great player for such a long time, that's the hardest thing. Even when he was ageing, when it's hard and challenging, he found a way. He hasn’t just impressed me, he's impressed everybody."

Back then, first impressions were important for Simpson. Handed the No.6 jumper, he was sandwiched between the lockers of two of the club's all-time greats. Ratten, in the No.7, was sat to his left. Andrew McKay, in the No.5, was sat to his right.

Ratten would be his first captain at the club, McKay would be his second, with the former handing over the reins to his deputy midway through that 2003 season when he retired due to persistent injury problems.

Those close to Simpson recall his younger self being slightly daunted by the position of his new locker. If being placed right between two club champions and premiership players wasn't already intimidating enough, then making your mark on your first two captains certainly was.

Needless to say, across 18 years and 342 games, Simpson certainly made his mark. And then some.

"It's quite mindboggling to think that he was there when I was playing, because it feels like a lifetime ago when I was playing … crikey," McKay tells AFL.com.au.

"For him to still be playing – and still playing good football, because he hasn't lost that consistency – it's really admirable. He hasn't tapered off at all. He has probably always been the first name that the coach has put on the magnet board and that's because he is so reliable and so consistent.

"If you looked at how he played the game, you'd say to every young fella coming through that if you can display those traits going out on the park each week, then you're going to go a long way to having a successful career.

"No one expects to play for that long. He's certainly made a huge imprint on all of the guys he's played with and all of the fans who have supported Carlton along the way. It's just a credit to him, I can't praise him enough for it.

"I saw the photo of him, Bruce Doull, Craig Bradley, Stephen Silvagni and big John Nicholls on Twitter earlier this week. They were phenomenal players, all of those guys. For Simmo to be sitting in that group, it's just so apt. He fits in perfectly with those guys."

Forget about the early starts back in 2003, though. And forget about questioning whether Simpson's mindset would alter when he found his place at the club, long after both Ratten and McKay had departed as players.

As Carlton's AFLW team filtered into Ikon Park in the fading hours of the summer sun for one of their late-afternoon training sessions last November, long after every other men's player had left, there was Simpson and the club's high-performance boss Andrew Russell.

Running strenuously timed laps around the boundary, Simpson was still going. The 18th pre-season was being attacked just as hard as the first, and Carlton's warrior was just as determined to keep putting the hours in. A total of 151 players made their Carlton debuts between Simpson's first game and his last, but few worked as hard.

In nearly two decades at the club, that version of Simpson has never gone anywhere. He is still as devoted, still as dedicated and still as fiercely loyal as ever. If you think his first two captains were impressed, his last two will farewell Simpson on Saturday night full of just as much admiration, if not more.

"I remember when I first got to the club, one of the first things I wanted to do was earn the respect of Simmo," Carlton's current co-captain Sam Docherty tells AFL.com.au.

"I've watched everything he's done and followed every move he's made. Across these years, and as we've played more and more footy together, we've always been competing against each other in time trials, running, our footy. I definitely think I'm a better player because of how hard he's made me push myself.

"The thing I've always admired the most about him is that when the game is there to be won, he's always there to make a last-ditch effort or put his body on the line or run that extra mile to get the ball and get it going our way. They're the people you want to play with."

The stories of Simpson's unwavering attitude and application off the field speak volumes for why the veteran defender is held in such high regard by everyone at Carlton. But his courage and skill on the field speak just as highly for the respect and recognition he has gained across the entire competition.

Initially played as a small forward, the story goes that Simpson's first coach at Carlton, Denis Pagan, shifted him into the backline just so he could get a kick. Held without a disposal in his first three AFL games, Pagan recalled back in 2016 saying to the bench: "For crying out loud, let him take the kick-ins … just get him a kick!"

There, at half-back, he has become one of the most reliable, durable and consistent running defenders of his generation. Last season was his 11th successive season where he averaged more than 20 disposals per game, in a career that has featured a Blues best and fairest in 2013 and seven more top-five finishes.

His poise and composure on his preferred left side has arguably become the trademark of his game. But it's the bravery and toughness required to consistently put a frame weighing just 75kg in front of some of the competition's most imposing key forwards that Simpson will be remembered for.

"Everyone who has played with Simmo would say the same thing … for someone so small in stature, he's got that much courage," Carlton's other co-captain Patrick Cripps tells AFL.com.au.

"That courage shows out on the footy field. He goes from being a really quiet, softly spoken person off the field, to a really aggressive leader on the field. It's just amazing to play with him.

"It's got a lot to do with being courageous, but it's also about him being smart. He's so detailed. He does have those acts that are just so brave, but if you watch him closely you can see the detail in everything he does."

Saturday night will be Simpson's 342nd and final game for Carlton. He'll depart the club as its third most capped player, behind only Craig Bradley (375 games) and Bruce Doull (356 games).

But the legacy he will leave at Princes Park, all of those years after arriving early for his first day at the club, will be much, much greater than simply the number of times he has run out in the Navy Blue.

"We've talked about this as a group, but he's a Carlton legend," Cripps says.

"The word 'legend' suits the way he's played for so long, and it will suit the way he'll go out.

"He's been a role model for so many people … for Carlton supporters, for players and even across the whole competition. He's been the heart and soul of this footy club."