ONE OF the Sydney Swans' most reliable, consistent defenders, Nick Smith admits he still harbours ambitions of moving back into the midfield.

Unfortunately for the 25-year-old, it won't be happening anytime soon, and certainly not when the Swans take on Carlton's mosquito fleet of Eddie Betts, Chris Yarran and Jeff Garlett in Saturday night's semi-final.

A no-fuss defender who is rarely beaten, Smith has carved out an excellent career nullifying Steve Johnson, Cyril Rioli and the rest of the AFL's most talented smaller forwards.

Swans coach John Longmire regularly jokes he wouldn't like to be Smith the night before a game, as sleep would be next to impossible as he contemplates his upcoming task.

The former Oakleigh Charger hopes the rest of his career isn't set in stone just yet.

"I played a bit of a tagger through the midfield in my third or fourth season and then got shifted back," Smith said.

"Hopefully I'm not too pigeon-holed yet into just being a defender and can hopefully get into the midfield again.

"But we'll leave that up to ‘Horse’ (Longmire).

"It'll depend on the balance of the team – how many mids we have, how many backs we have, where I can best be used for the team."

For now, that is undoubtedly in the Swans' well-drilled backline that will have its hands full against the Blues.

Betts has returned to form in recent weeks, kicking three goals in Carlton's stirring comeback victory over Richmond last Sunday.

Garlett has kicked 43 goals for the year, including two against the Tigers last week, while Yarran provides plenty of run from halfback and has still managed 26 goals himself in 2013.

"I thought they were a big impact in getting the Blues back into the game (against Richmond)," Smith said.

"They were the first to admit they started a bit slowly, but they definitely changed the momentum, and some of those small guys really gave them a lift.

"It'll be probably Betts or Garlett (that I'll be defending), or a mixture of both.

"(Betts) is a really good player. If you're not switched on, he'll definitely get a hold of you, which has happened before.

"He can get the ball on the lead and go for his grabs, as well as being a really good crumber.

"He's good in general play as well, so he's got a few strings to his bow."

Wary of Carlton's attacking weapons, Longmire is also mindful of Chris Judd, Bryce Gibbs and Marc Murphy, who regularly gave the Blues first use of the ball last week.

The coach is grateful he can call upon Smith, a member of the Swans' leadership group who took out the 'Best Clubman' award in last year's premiership-winning season.

"Nick has played well on some of the opposition's best small forwards and has a history of it over the last number of years," Longmire said.

"He gets the tough jobs (and) this week we come up against some of the best.

"For Nick Smith, Dane Rampe, those types that will be playing on the opposition's best smalls, it's a challenge."

Whether or not he ends up back in the midfield down the track, Smith feels he still has plenty of improvement left in him.

"Most players as they get older tend to improve," he said.

"Being a defender you become a lot smarter reading the play, where to run, how to defend different types of players as well as getting fitter and stronger.

"You definitely improve."