South Sydney five-eighth Luke Keary has dared Canterbury's imposing forward pack to test his supposed defensive frailties in Sunday's NRL grand final.

Once rejected as too small to play in the NRL, Keary's late-season halves combination with Adam Reynolds has sparked the Rabbitohs attack and helped to send them into their first grand final in 43 years.

Keary has been targeted as a weak link in Souths' defence line since his return two months ago from a pre-season pectoral injury suffered in the Auckland Nines.

He again expects plenty of treatment from the massive Bulldogs pack on Sunday, but says he welcomes the challenge.

"Defensively I try to play with a bit of a chip on my shoulder. I don't want any big fella to think I'm an easy beat or they can run straight over me," Keary said.

"Being a little fella there you are going to get a bit of traffic and they are no different, they have one of the biggest forward packs in the competition.

"Big T-Rex [Tony Williams] and Frankie [Pritchard] and Josh Jackson, who is in great form, will be going down at us on that edge.

"I pride myself on my defence and I think it is a massive part of every half's game having to be able to stand there, win your tackles and be strong defensively, otherwise you're going to be targeted and it is going to affect the way you play footy."

The 2014 decider is a game Keary, who made his NRL debut last season and has notched up 21 games, thought he would never play after being injured at the inaugural Nines tournament.

"When I first did it, it didn't really hurt too much, but I knew I had done my pec and thought that was the end of the season," he said.

"Fortunately it was only four months, but it was a pretty tough four months.

"We have a really good staff here who helped me through that.

"Madge [coach Michael Maguire] always said if I worked hard and did the right thing my opportunities would come.

"Whether it was going to be this year, whether it was going to be next year my opportunity would come.

"Fortunately it did come and me and 'Reyno' have struck up a bit of a combination there and we are running with momentum at the moment.

AAP