One mark was all it took to convince Simon Goodwin not to substitute young forward Jacob van Rooyen out of Melbourne's clash with Richmond.

The 20-year-old had a team-low four touches and little impact to three-quarter time on Monday night.

But his soaring grab on the shoulders of Noah Balta early in the decisive final term changed Goodwin's mind.

"He took one mark," the coach explained.

"He was pretty much coming off at his next rotation - we were about to sub him out.

"Then he took a couple of clunks and we said, 'Keep going, son. You're away now.'"

Van Rooyen's subsequent goal and another four minutes later gave Melbourne a 16-point lead after they had trailed Tigers by 25 during the second term.

The rising star held his nerve with three of his four set shots in the last quarter and capped his match-winning cameo with the Demons' sealer.

"We've been working with Jacob about staying in the now," Goodwin said.

"It might not be your moment right now but you'll have one later on, and he had a really good last quarter."

The No.19 draft pick in 2021, van Rooyen had to bide his time in Melbourne's reserves side last year as he developed.

He kicked three goals on his AFL debut in round three this season and has now kicked nine in four appearances.

"We put a lot of expectation on young key forwards and he's still finding his way at AFL level," Goodwin said.

"He's only played (four) games of AFL footy so he's just going to continue to build and get better and better.

"He's going to need the experience of guys around him and he'll have games where he doesn't impact like tonight for three quarters.

"But over time we've got someone who we think will continue to evolve into a really good AFL player for us."