Ross has been cleared of a fractured back after the former Queensland prop heard "a crack" when three forwards landed on his head as he completed a tackle late in Cronulla's 18-10 defeat of Penrith on Saturday night.

He will remain in hospital for a few days under observation and is waiting to see a spinal specialist.

Fullback Kearney is another serious injury concern as his right ankle injury appears to be a bone separation problem that could rule him out of football for three to four months.

He will have scans on Monday.

The injury news is a cruel blow to Cronulla after the club made a determined start to 2009 with some gritty defence against a wasteful Panthers side.

Test forward Anthony Tupou, who was brought to Cronulla for what he can do with the ball in hand, said he felt he owed it to his new teammates to live up to their high defensive standards.

The former Rooster certainly muscled up in defence with an eighth minute bell-ringer on Brad Tighe that left the Penrith centre dazed It is that level of intensity in defence, and commitment on the goal-line, that Tupou believes he needs to deliver in 2009 to meet the high standards set by the Sharks throughout 2008.

Cronulla repelled continuous tryline attacks from Penrith at Toyota Stadium on Saturday night that forced the Panthers into inexplicably kicking on first, second or third tackles.

"We've got that sort of team where everyone is pretty close," said Tupou of their defensive commitment.

"I've told them all that I feel lucky to be part of that and have walked into that so I can't let them down in that way.

"I have to sort of match their defence." Tupou's biggest influence at Cronulla is likely to come from his attack and he showed glimpses of that too with a crucial four-pointer in the 55th minute that gave Cronulla a lead they never relinquished in a 18-10 defeat of Penrith.

The try brought most delight to coach Ricky Stuart as it featured the big three from Cronulla combining for points.

New five-eighth Trent Barrett threw a brilliant and flat cut out pass for skipper Paul Gallen to burst through the line and then flick an inside pass for Tupou to score untouched.

Tupou said he was hopeful his left-hand side attack with Gallen would become a feature of Cronulla's play in 2009.

"Gal works both sides and does it well but I love it when he is over my side," said Tupou.

"It feels comfortable and it feels like we are more of a threat.

"I was pretty happy to score a try. I didn't do much to get it but I'm off the mark now.

"We played pretty poorly and I don't think anyone is too happy with the game only just happy with the two points.

"We were just awful and we've got to fix that."

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