ONE of Leon Cameron's biggest selection calls for Sunday's round one clash with the Western Bulldogs surrounds Greater Western Sydney's two biggest players.

In one corner, the athletic Rory Lobb, a contested marking key forward looking to take over the mantle from the retired Shane Mumford as the Giants' number one ruckman in 2018.

In the other, the resilient Dawson Simpson, a journeyman who has played just 30 games of senior footy at Geelong and GWS since being drafted way back in 2007.

There's little doubt Lobb holds the advantage in terms of his athletic ability and marking power, but the West Australian has battled groin issues over summer and only had one NEAFL scratch match to prepare for the season, so he's sure to be underdone.

Simpson gives the Giants a huge mass of a man who provides enormous strength around stoppages and gets his hand on the footy first at most ruck situations.

However, he can be exploited by more mobile opposition big men such as Jackson Trengove or Jordan Roughead, whom he could come up against on Sunday afternoon.

Which way Cameron leans is anyone's guess at this stage, and Mumford, in his new role as GWS ruck coach, wasn't giving anything away when he fronted the media at UNSW Canberra Oval on Tuesday.  

"I think 'Lobby' is putting his best foot forward, but he's got a real challenge on his hands because Dawson Simpson has been playing really well," he said.

"As for who gets to play I'm not too sure just yet. It's certainly going to be an interesting match committee trying to work out who to pick.

"I think these guys will step up, whether it's Rory Lobb or Dawson Simpson, whoever gets a game I expect them to be really demanding of the midfielders and getting the best out of them."

The ruck battle will prove crucial in the season opener, with both sides expected to bring full strength midfield divisions to the nation's capital.

Giants Josh Kelly, Stephen Coniglio, Callan Ward and Dylan Shiel give Cameron a star-studded onball quartet, but with Marcus Bontempelli, Jack Macrae, Tom Liberatore and Toby McLean in form, the Dogs are also stacked with talent.