Sydney coach Paul Roos says the gap between TAC Cup and AFL is massive and No.6 draft pick Gary Rohan can forget about making his debut for the Swans in 2010.

"I'd be staggered if he played senior footy next year," Roos told AAP on Friday after returning from the national draft in Melbourne.

Rohan has emerged as another shining light in the Geelong Falcons under-18 program, Falcons general manager Michael Turner declaring he's the most exciting prospect he's seen.

But Roos was quick to play down the hype surrounding the 18-year-old key forward from a dairy farm near Cobden in Victoria's western district.

"That's where you have to be careful players don't have unrealistic expectations," Roos said.

Rohan, East Fremantle recruit Lewis Jetta, ex-Murray Bushranger Sam Reid, Byron Sumner from Woodville-West Torrens, Subiaco goalsneak Trent Dennis-Lane and Swans rookie elevation Kristin Thornton will learn quickly on the training track about the demands of playing AFL.

It's a lesson Sydney's co-captains Brett Kirk, Craig Bolton and Adam Goodes are willing to hand out at every opportunity with the examples they set on the sandhills, in the gym and on the field.

"They learn pretty quickly. It can be like hitting a brick wall," Roos said.

"The youngsters get really shattered by what it takes to be an AFL player.

"It will happen to Gary Rohan.

"He has got a lot of work to do. He's very raw.

"He only averages 12 possessions a game.

"These guys coming from under-18s are super-talented, but ... the gap is massive."

Roos says 20-year-old Patrick Veszpremi, an exciting forward who has played 10 senior games, is still finding his way.

"In his running, he's a mile behind Kirky and (2009 club champion) Ryan O'Keefe," Roos said.

"All our younger guys face a reality check.

"No question Kirky (aged 33) is still one of our best on the pre-season training."

Roos said with youngsters on the Swans list still developing, it was important to bring in ready-made senior players like Shane Mumford (ex-Geelong), Mark Seaby (ex-West Coast), Daniel Bradshaw (ex-Brisbane), former Hawks Josh Kennedy and Ben McGlynn and Swans premiership halfback Tadhg Kennelly, back after a year playing Gaelic football in Ireland.

Roos is hopeful Jetta, Sydney's second selection and No.14 pick overall, can play AFL next year.

"He has got some special talents. But he's still very light at 69 kilograms," Roos said of the 20-year-old.

"What you don't want to do is take away that lightning speed.

"Is it four kilos more (required)? I don't know."

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