Canterbury's Tim Lafai may have had a memorable NRL debut with a crucial try against South Sydney on Sunday, but fans won't be seeing the raised arm celebration again.

At least not before he has safely grounded the ball.

The 19-year-old former Souths junior was called into the Dogs starting side for injured centre Josh Morris on Wednesday and signalled to the crowd before touching down for the 72nd minute try that sealed the deal.

"He won't do it again," said otherwise pleased Canterbury coach Kevin Moore.

Lafai, who is set for a lengthy stint in first grade with Morris sidelined until round seven, definitely got the message.

"I think everyone, the whole coaching staff, just warned me to put it down first," he said.

It was a sure sign the Samoa-born youngster, who was scouted by the Bulldogs from East Campbelltown, felt at home in the top grade.

"I felt heaps comfortable out there because I've been training (with) first grade in the off-season and they've just helped me heaps, all the senior blokes, they were good out there helping me," he said.

Canterbury captain Andrew Ryan said Lafai had impressed during the trials.

"He didn't look overawed at all and then today he just came out and, obviously he was pretty nervous before the game, but he'll get a lot of confidence out of that," Ryan said.

"He's a pretty quiet sort of kid but he just backs himself and that's what you want, you want someone who's going to come into first grade and back themselves."

As long as they put the ball down first.

"I'm pretty quiet off the field but once I'm on the field I've got to be loud," Lafai said.

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