The challenge of winning back-to-back NRL titles is so immense that Issac Luke insists South Sydney are not thinking about it.

No team since the great Brisbane outfit featuring the likes of Steve Renouf, Allan Langer, Kevin and Kerrod Walters and Glenn Lazarus, among a raft of other stars, has successfully defended their premiership in a united competition since 1993.

Melbourne and Manly dominated for a decade and threatened to build dynasties but still couldn’t manage two grand final wins in a row.

The Sydney Roosters reached six title deciders in 13 seasons, but they couldn’t muster successive premierships.

It’s such a tall order that Luke says it’s not worth contemplating little more than two months after the Rabbitohs broke their 43-year title drought with their victory over Canterbury in the 2014 grand final.

“We haven’t really been thinking about that,” Luke said at Thursday’s launch of the Auckland Nines in Sydney.

“We’re obviously worrying about our own preparation in the pre-season.

“I mean, everyone in the competition is hopefully getting themselves ready to get there at the end of the year.

“All I know is `Madge’ (coach Michael Maguire) will be drilling into the boys just to take it week by week.”

Luke suffered the anguish of missing Souths’ historic win over the Bulldogs after failing to have his dangerous throw charge overturned at the NRL judiciary earlier in the week.

The New Zealand Test hooker said he had moved on from the disappointment and gained some consolation last month when he helped the Kiwis to Four Nations glory over Australia.