Sydney coach Paul Roos has drawn a line in the sand with the mooted western Sydney AFL side, saying the Swans want the expansion club to flounder.

The premiership-winning coach shelved his nice guy persona and showed there wouldn't be any love coming from his club for the new franchise, due to debut in the 2012 season.

"Let's make one thing absolutely clear - expansion is not a Swans initiative," Roos wrote in his column for News Limited.

"We are not involved in the western Sydney team and we have nothing to do with the process.

"But suddenly the Swans are supposed to be the PR machine flying the flag for future cross-town rivals.

"On the contrary, if a second Sydney team does come into the league they will be our bitter enemy.

"We are the Sydney Swans Football Club and we need to do as much as we can to make sure our brand is impregnable when the second team is launched."

Roos said the Swans would be on their guard against poaching from their potential crosstown rivals.

"Our goal is to crush them as an opposition team," said Roos.

"We won't be sympathetic to their cause and we will be hoping they'll finish on the bottom of the ladder.

"We will be hoping we beat them by 100 points every time we play them and we won't let them poach any of our players.

"I'm certain we'll have an instant dislike for them and won't cut them any slack."

Roos pointed out the massive financial troubles of the Cronulla Sharks in the NRL as evidence of the challenges of competing in the Sydney sporting market.

"Not every club can be like Collingwood or West Coast and have the ability to generate enormous amounts of money to make themselves effectively bulletproof," he wrote.

"The rest of us continue to fight tooth and nail to stay in the black."

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