Six months ago Cronulla coach Shane Flanagan felt Nathan Gardner was too small to cut it in the NRL.

But after another match-winning display against Sydney Roosters on Friday, Flanagan is now the 20-year-old fullback's biggest fan and predicted a bright future for the former Parramatta junior.

Gardner, who made a tryscoring debut against Penrith in round 10, scored the decisive four-pointer in his side's shock 18-12 win over the high-flying Roosters, who tasted defeat to the Sharks for the second time this season, following their 42-18 humbling in June.

"He was outstanding again and I have to say I was one of those who question marked whether he was big enough to play in the NRL," Flanagan said.

"But he is one of the toughest players for his size I have ever seen.

"He is going to be fullback for the Sharks for a very long time which is great because we haven't had one for a while."

Gardner, who also scored one of the tries of the season when the two sides last met at the Sydney Football Stadium, finished the game battered and bruised, with Braith Anasta and Frank-Paul Nu'uausala put on report for high shots on the jet-heeled five-foot-six flyer.

"I am a bit sore but it doesn't hurt so much when you win," Gardener said.

"I seem to do well playing against the Roosters I guess they have been lucky opponents for me.

"I came here to Cronulla to get the chance to play first grade and I am enjoying every minute of it. It has been a tough season but wins like this make it all worthwhile."

The win was Flanagan's first since taking over from Ricky Stuart last month and he believes if his side's can improve their attacking prowess to match the brilliant defence they showed to keep out the Roosters, then the future is bright.

"There is so much character in this bunch of guys, they defended for their lives tonight," he said.

"In the first half our attack was poor but we were a lot better in the second and I believe if we can improve that we will be a very good side in the future."

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