Now, having played 43 games in the past two seasons and with the support and belief of coach Scott Watters, Armitage is in the club's leadership group and is becoming an important part of the midfield set-up.
Back in 2010, Armitage played nine games and suffered a knee injury in the second half of the season that saw him not picked for the finals.
His luck was better in 2011, but when Watters arrived at the club that October he wasted no time emphasising that Armitage had to improve.
"There was probably a very early juncture with 'Armo' and I having a conversation, just on his level of professionalism and what he needed to do to actually fulfil his potential and promise," Watters told AFL.com.au.
"He really took that on board and from that point, I thought his understanding of what it was going to take for him to elevate himself as a player, the standards he needed to train at and the way he needed to view his overall presentation and preparation, there was a significant change."
Armitage was drafted at No.9 overall in the 2006 NAB AFL Draft but struggled to hold down a senior spot in the early stages of his career.
"A lot of the time in my first four or five years I always doubted myself and didn't think I was good enough to play," he said.
"I just accepted being a fringe player and I was just happy to be a fringe player.
"Then as you get older, you start to think, 'I don't really want to be this – I either want to play or I don't'."
He played 22 games in 2011, but admitted he struggled to run out games and lacked the fitness to make a consistent impact.
Last year he played 21 games but was rested in round 22 and spent more time in the forward line as he tired towards the season's end.
Still, he felt better about himself. As Watters' influence took root he began to feel more comfortable at senior level.
"He really gave me confidence and coming from another club, he told me he'd rated me from outside," Armitage said.
"Just at training, if I made a mistake I was ready for a spray and he just pulled me aside – and he did that with a lot of blokes, Sean Dempster, Jimmy Gwilt – and said, 'I'm not going to get up you if you make a mistake, as long as you make a mistake and try to do something good'.
"I started to back myself in a bit more and hit different kicks and it started paying off.
"You need confidence as a player otherwise you're going to drop your head and it will just start creeping in and eats away at you."
Watters said the credit belonged to Armitage for changing his approach. The 24-year-old now pays more attention to one percenters and the little things when away from the club.
Front and centre: David Armitage (third from left) has earned his place in St Kilda's midfield. Picture: AFL Media
The hard-bodied midfielder can improve again this year, Watters said, after a pre-season that has left him in "terrific nick".
"Sometimes as a coach you have to make sure the player knows you have a vision for them and that you're prepared to walk alongside them to get them to that point," Watters said.
"I believe in him as a player but ultimately he's been responsible for forging forward.
"I certainly have a lot of faith that he can still get better, as well."
Armitage will enter this season fitter and stronger after a pre-season that started with what he believes was a hugely beneficial altitude training trip to Colorado in November and December.
His NAB Cup outings have already demonstrated his physical improvement.
"I normally cramp and I'm not able to run out games at this time of the year," Armitage said.
"It's something I've struggled with in the past. Now, I've run out third and fourth quarters like it was the first and second quarters.
"In the last two years I've really worked hard on my footy and the professional side of things.
"I had a really good season last year but I can't get happy with that. I've got to go one better this year and I'm really looking forward to that."
David Armitage is a midfielder in NAB AFL Fantasy. He averaged 89.19 points in 2012. Register your team at our AFL Fantasy Hub.
Jennifer Phelan is a reporter for AFL Media. Follow her on Twitter @AFL_JenPhelan.
