IT WASN'T that long ago Zac Smith was being touted as one of the best young ruck prospects in the AFL.

With his unique combination of size – 205cm and 100kg – athleticism and skill, the Gold Coast giant had observers salivating after an eye-catching debut season in 2011.

But after some patchy form in 2012, a ruptured ACL early in 2013, and a serious ankle injury 10 games into last year, the quietly-spoken Smith slid down the Suns' pecking order. 

On the verge of turning 25 and entering his fifth season, the Queenslander is well aware of the significance of 2015.

"It's a very big year for myself. I'm not shying away from that," Smith told AFL.com.au.

"I'm really confident and really positive going into this year and I can't wait to see what happens."

The ruck division at the Suns is a talented one but rarely has a single player been the No.1 option for long.

Smith is in a dogfight with Tom Nicholls, also on the comeback from a long-term posterior cruciate ligament injury, for the mantle of top dog, with the athletic Daniel Gorringe putting in a strong pre-season to also press his claims.

Gorringe seeks midfield time to prove himself

Smith has completed every session since the week prior to Christmas and said it was the first time all three ruckmen had been able to push each other at training.

In a modified match simulation on Friday, Smith and Nicholls held nothing back at either centre-square or around-the-ground duels.

"The competition this pre-season between us rucks has been really good and we haven't had that in previous years," Smith said.

"Neither one of us has had to really fight for a position, because we've all been injured, so it's been good to fight against these big boys, and (rookie) Keegan Brooksby.

"I feel really good, probably the best I have in a couple of years, since before my knee (injury)."

While it shapes as a battle between Smith and Nicholls, Smith said he hoped the Suns would play two specialist ruckmen during the season. 

Coach Rodney Eade might get his chance to trial the option during the NAB Challenge opener against Geelong on February 28, with the Suns' tall timber department severely depleted.

Charlie Dixon (ankle), Rory Thompson (turf toe), Sam Day (calf) and Steven May (knee) are all unlikely to play, leaving the door open for the rucks to rotate.

When fit, Dixon has played as the Suns' forward/ruck back-up, but Smith likes the idea of working over the opposition with two specialists.

"I really want to build a ruck combination that other teams are afraid of," Smith said. 

Zac Smith is a $366,000 ruckman in NAB AFL Fantasy this year. Create and fill your AFL Fantasy Classic league by March 2 to win a free AFL Live pass.