AFTER his team's round 15 loss to St Kilda, North Melbourne coach Brad Scott said Lachie Hansen and Cameron Pedersen were key-position players with the versatility to play at either end of the ground.

Against the Saints, Hansen, who had spent nearly all of this season in attack, spent the first half manning St Kilda captain Nick Riewoldt.

At the other end of the ground, Pedersen, who had played in the ruck, defence and attack since being elevated from North’s rookie list before round one, was stationed in the forward 50, alongside Drew Petrie and Aaron Edwards.

Although Hansen impressed with his one-on-one efforts against Riewoldt, he conceded three second-quarter goals as the Saints midfield got on top.

Meanwhile, Pedersen had kicked one goal from limited opportunities.    

With St Kilda 20 points up at half-time, Scott switched Hansen and Pedersen.

The move proved a good one, as Pedersen kept Riewoldt scoreless in the second half and Hansen gave North a target up forward and kicked a goal.

Having such versatile key-position players obviously gives a team added flexibility in matches.

Essendon's Michael Hurley is another player who has proven just as effective in attack as down back, while Carlton’s Lachie Henderson, who has spent most of his four-season career in attack, has competed strongly as a key defender in the past two rounds in Michael Jamison’s absence. 

Defenders Chris Tarrant (Collingwood), Luke McPharlin (Fremantle) and Bret Thornton (Carlton) have also shown they can perform in attack when required.

But not every tall is capable of moving from one end of the ground to the other. And those who can, generally have to work hard on the training track to ensure they can fit in with the vastly different team expectations on defenders and forwards.

North Melbourne assistant coach Darren Crocker said Hansen and Pedersen split their specific group training time between the defensive and forward groups, with Hansen spending about 70 per cent of his time with the forwards and Pederson about 70 per cent of his time with the defenders.

"They need to learn the leading patterns as a forward, whether that’s creating space or being on the end of passes," Crocker said. 

"And, as defenders, they need to know when to defend really strongly, when to take the proactive position, when to press up and when to come off their opponent and go third-man up.

"They are two very different roles but two super-important roles. There are some players who've got the understanding and capabilities to be able to play both. And then there are guys who are just suited to playing one role."

Carlton assistant coach Gavin Brown said although Henderson's move to defence had been born out of necessity, he had the attributes to play a key position at either end of the ground.

"He’s got the big body you need because you’re going to be in a lot of contests," Brown said.

"I think those type of players have also got to be pretty good readers of the game. It’s a completely different game up forward to what it is down back.

"One minute you're leading at the footy to create space, the next you're working out how to shut down the space of the opposition forwards.

"So they've got to be comfortable with that and good concentrators because things can change dramatically from one end to the other.

"The other thing is you want your key position players to be able to use the footy well and Lachie ticks that box as well."

Above all, Brown said players had to embrace the challenge of leading a nomadic key-position existence.

"Some players cope better than others and they're the ones who work and you'll always go back to," Brown said.

"You try some and they don't work because they prefer one position to the other, they're not comfortable or they can't switch their focus."