After a season to forget, it comes as no surprise that Sydney defender Aliir Aliir is keen to leave 2017 behind him and throw all his energy at the future.

The athletic Swan played three of the first four games of last season but wasn't seen at senior level again, after Lewis Melican debuted in round five and consolidated his spot in the League's most miserly defence.

When he did play, Aliir looked nothing like the player who had been an important part of the Sydney backline in the second half of 2016, with a pre-season toe injury hampering his preparation, and some ill-discipline not helping his cause.

Dropped after the Swans' round four loss to West Coast, Aliir earned a recall after two solid outings in the NEAFL, but missed a training session the day before the team's round seven clash with the Brisbane Lions, and was axed again.

The 23-year-old spent the rest of the year in the reserves, which seemed a waste for such an exciting prospect, but it was a clear message from the Swans that past performances and talent come a distant second to the famed Bloods culture.

Aliir told AFL.com.au that the past 12 months have been challenging and he was disappointed with how things worked out, but he wouldn't let it affect his 2018 season.

"Last year didn't go my way, I wanted to be out there and it was tough to watch," he said.

"I want to be playing at the top level every week so it was disappointing, but I can't dwell on it too much - that’s footy and these things happen.

"My focus is solely on making sure I'm out on the track for every session and improving week by week, and I'm really looking forward to the year ahead."

Despite the emergence of Melican, and the continued form of veteran Heath Grundy and 2016 All Australian Dane Rampe, Aliir is confident he can once again break into the Swans' backline group.

"I definitely think I can but I'm not looking too far ahead," he said.

"I just want to keep working hard on my defensive stuff at training, because that’s my job, to defend my opponent first.

"I'm working closely with guys like 'Reg' (Grundy) and 'Ramps' (Rampe), along with the backline coaches, asking them constantly about little things I can do to improve."

Some might expect Aliir to be obsessed with lifting heavy and adding bulk to his frame to allow him to take on the competition's power forwards if needed, but that’s far from the case.

Describing his weight as "perfect", Aliir said he was desperate to keep the agility that has helped him be successful in the past.

"I've actually been challenging myself to play on guys like Kieren Jack at training because these days you have to be able to play on bigs and smalls," he said.

"There are times when I might get caught up the ground on someone like (Paul) Puopolo or (Cyril) Rioli, so it's just about developing and learning to play on different guys, and I think I can do the job on smaller players as well. 

"They're much quicker than me - one second they're there, the next second they're gone, but the more I challenge myself at training the better I'll be on game day."