Sydney’s trump card this AFL season could come from none of the side’s new faces, but rather a fit-again Kieren Jack.

Jack went from his club’s best player to small beer in 2011.

He injured his right ankle in round six – midway through a fine shutdown job on Carlton captain Chris Judd – and returned but never recovered.

“He’s one of our real key players. He works hard both ways,” Swans coach John Longmire says.

“People tend to forget that two years ago he won our best and fairest. Last year he did his ankle, missed six weeks then came back and did it again.”

Jack won’t forget his first injury-plagued season in a hurry.

“Last year for me was pretty frustrating. It was the first time in my career I’d really been injured,” he told AAP.

“I didn’t need any surgery (after the season) … the ligament that I tore in my ankle, the only real surgery you can do is put a screw straight through it.

“So that was something we wanted to steer clear from.”

The midfielder was instead told to focus on rest – a welcome change after playing through the pain last year.

“Certainly I needed some time off just to let it heal,” he said.

“I think last year, when I came back and played again – week in, week out – it sort of never fully recovered.

“I just needed some time off. I spent time with some family and friends and really got away from football for a little bit.

“But now I’ve got 100 per cent confidence it’s back to normal.”

And it already shows.

The 24-year-old has made a bright start to the Swans’ pre-season campaign after doing all the hard work over summer.

He looked back to his hard-running best in clashes with St Kilda and North Melbourne.

Jack was substituted off in the second quarter of his side’s last-start clash with Essendon as a precautionary measure after a knock to his leg.

But the club is confident it’s nothing serious and hopeful he’ll play Gold Coast on Saturday.

After the troubles he faced last season, Jack knows that’s something worth cherishing.

“It’s made me appreciate being healthy, being fit and playing consistent footy every week,” Jack said of his curtailed 2011 campaign.

“I had the rest and really worked hard in the pre-season, just getting my fitness back and getting my movement back to where it was in previous years.

“I think I’ve been able to do that, so I’m looking forward to getting into round one.”