POPULAR young Tiger Ryan Garthwaite will remain at the club until at least the end of 2019 after quietly signing a one-year contract extension earlier this year.

AFL.com.au understands the 19-year-old, who made his AFL debut on Sunday against Geelong, inked the new deal about two months ago.

He was a late inclusion into Sunday's side after fellow defender Davis Astbury failed to recover from the ankle he injured against Port Adelaide in round 12.

Coach Damien Hardwick said after the game it had been a bonus for the premiers to unveil a second debutant for the season after Jack Higgins played his first game in round three.

"To see young Garthwaite come in, he's a very popular member of our footy club, one for his character but two for his incredible work-rate, the way he approaches his training," Hardwick said.

"For a first-game player to play on one of the premier forwards in the competition, he'll certainly learn a lot.

"We've always known he's going to be a pretty good player, he's a David Astbury-type clone."

Garthwaite played on Tom Hawkins at times and overcame a shaky start to hold his own against the experienced Cat.

The backman was drafted from the Murray Bushrangers at pick No.72 in the 2016 NAB AFL Draft and spent his first year at the club developing in the VFL.

He hails from the New South Wales Riverina town of Corowa and has made a big impression on his Richmond teammates in 18 months.

Club captain Trent Cotchin this week told richmondfc.com.au he was the type of person "you'd want to marry your daughter" and Jack Riewoldt said he was the "nicest bloke you'll ever meet".

Defender Nick Vlastuin told a story about how his teammate reacted when his car was stolen.

"He used to drive a Ford Sapphire, I think it was called – a real old, beat up car," Vlastuin said.

"Then, some dude stole it and crashed it into a tree.

"There was a bit of blood left in the car and 'Garth' was actually worried about how the guy was, rather than his car."