Following a limited pre-season, Armstrong's opportunities in his first year with the Swans came only when he was replacing either an injured or suspended teammate.
In 2013, the former Adelaide Crow is determined to earn a place in the team in his own right, starting with a strong showing in the NAB Cup.
"It was a good first 12 months," Armstrong told AFL.com.au of his move to Sydney.
"At this stage last year I'd only just started training with the group, so I was a fair bit behind.
"With a team that eventually won (a premiership), it was hard. I always felt like I was taking someone else's spot, rather than making the spot my own.
"If I'd started in the team it would've been different.
"But it was a great first 12 months. I came to a team that won a flag. It doesn't get much better than that."
The only thing better, of course, would be playing in a premiership himself and Armstrong came about as close as possible last year.
Replacing the injured Nick Smith for the round 23 clash with the Cats in Geelong, Armstrong played well, tallying 21 possessions in a 34-point loss.
It would be Armstrong's final appearance for the season, however, as he made way for Smith the following week.
Armstrong was then an emergency for each of the Swans' three finals matches, including the Grand Final.
"The spot was (Smith's), but it was still a great opportunity and I was really close to getting a berth in all the finals," he said.
"Looking at it as glass half-full, it was awesome to basically be that 23rd man in a premiership side."
Coach John Longmire confirmed just how close Armstrong was to playing in the finals and said the 23-year-old has a chance to press forsenior selection, starting with Sunday's NAB Cup game against St Kilda.
"He was very close. In conversations we were having in the last couple of weeks he was very close to getting a game in the finals," Longmire said.
"He played some good footy for us last year and has had a reasonable pre-season, so his baseline is pretty good.
"He just needs to take the opportunities in the upcoming games and really cement himself in the team."
With Rhyce Shaw, Marty Mattner and Nick Malceski sitting out this week, Armstrong has an ideal chance to push his claims.
"We've got a number of guys that can play that halfback, back pocket position and play it well," he said.
"I have to make the most of it (in the NAB Cup). All the fringe players do.
"I don't try to put too much pressure on myself and think I need to get 35 touches and all that sort of stuff.
"I just know that if I play my role and do all the team things, that will be what gets me a game."
James Dampney is a reporter for AFL.com.au. Follow him on Twitter: @AFL_JD
