MASTERING a new role on the run is never easy, and when your performance is being heavily scrutinised week in week out on the AFL stage, the pressure would be even more immense.

But if it's had an effect on Greater Western Sydney's Lachie Whitfield, he's got one hell of a poker face.

The 2012 No.1 draft pick played 90 games across his first five seasons, all of them as a free-wheeling wingman, but his 2018 season has elevated him to elite status – and his timing has been perfect.

The Giants lost their two best attacking small defenders when Nathan Wilson went back to Perth at the end of last season and Zac Williams ruptured his Achilles in January.

Coach Leon Cameron needed a replacement and went with his running machine Whitfield.

What's followed has been a remarkable season across half-back, and some extraordinary numbers.

The 24-year-old has played all 20 games this year, averaging a career-high 27.4 possessions at 78.1 per cent efficiency.

He's ranked first in the AFL for uncontested possessions and seventh for kicks.

Whitfield started the season well and averaged 25.1 touches across the first 10 games, but has gone to another level over the past 10, elevating his output to 29.7 touches in that time.

In five of those games he had 30-plus disposals, while the other five were all above 25.

It's little surprise that the Giants won nine of those 10 matches, jumping from 11th on the ladder to third.

Whitfield told AFL.com.au it's been a crazy five months adjusting to life in the back half.

"I was probably thrown in the deep end a little bit and was just learning how to swim at one stage there," he said.

"But the more I played with our backline the more confidence I got, and the more I learned about the role I was playing.

"I'm starting to run with the ball a bit more, I'm taking on harder kicks than I was earlier in the year, and my one-on-one defence has definitely improved as well.

"I'm feeling a lot more comfortable in the position."

Whitfield said the influence of GWS defensive coach Mark McVeigh and teammates Phil Davis and Heath Shaw has been important for his development this year, and his close mate Williams had also played a huge part.

"At half-time of most games Zac comes down and gives me 30 seconds of what I'm doing well, and what I could do better," he said.

"He's played my position a lot over the past three years and did it really well, so he's really helped me a lot.

"I know we're the same age and have played about the same amount of games, but he's a wise head when it comes to playing that role."

Shaw's season-ending knee injury was a massive blow for the Giants, but Whitfield intends to seek out his fellow backman for more mentorship for the rest of the year.

"He's a premiership player and someone with so much talent, so I'd be silly not to tap into his crazy brain," he said.

Whitfield will be a key player in this week's Sydney derby at Spotless Stadium, and he knows he could cop some extra attention form the Swans.

After Whitfield's blistering start to the season, Sydney stopper George Hewett held him to just 15 touches – including just five kicks – in round three, one of only two games in which he's gathered less than 22 possessions in 2018.

Hewett usually plies his craft in the midfield, but Whitfield is prepared if the tag comes his way again in round 22.

"First of all, I'm a defender, so my job is to beat my man one-on-one, so that's what I focus on," he said.

"After that it's about helping my teammates, whether it be creating two-on-ones or shutting down a player for a certain amount of time, so that's a way to deal with it.

"Plus, we've got Adam Kennedy back playing now, so we've got a few running defenders in our back half.

"If a team wants to sit on one of us, then another can get off the chain."