Filling in for Tom Trbojevic is a tall order at the best of times, let alone with a home semifinal potentially on the line.

The Manly talisman will miss this weekend's clash with Cronulla, where a win will deliver the Sea Eagles a clash at Brookvale Oval in the first week of the finals

Given that Trbojevic will nurse his shoulder injury through the rest of the season, finding the right replacement is crucial and the pressure on the new man at the back will be immense.

Fortunately for the Sea Eagles, rookie Lehi Hopoate doesn't seem to feel pressure, no matter what gets thrown his way.

Hopoate will vie with speedster Tolu Koula to line up at the back against the Sharks on Sunday but regardless of where he takes the field, his contributions have quickly become vital for Manly.

The 19-year-old has played fullback, left wing and right wing through an impressive maiden campaign that has yielded nine tries in 11 games this season, including two in Friday night's win over Canterbury.

"I was devastated [for Trbojevic[. He doesn't deserve any of this, he's such a hard worker," Hopoate said.

"Having a player like that in your team is such an advantage, he's probably the best fullback in the game right now.

"To have him as a teammate, to learn off him every week, every day, it's been big for my career.

"I'm just happy to be in the 17, wherever Seibs [coach Anthony Seibold] puts me, I'll take it with both hands."

Hopoate has risen to every challenge thrown his way this season and nothing seems to phase him — his first-grade debut came at fullback when he stood in for Trbojevic in an epic victory over Melbourne, which remains the finest win of Manly's season.

The Beacon Hill junior has made a belated charge for rookie of the year, averaging 139 metres a game and impressing with his composure and athleticism.

If he does stay on the wing, Manly will still rely on him heavily given Jason Saab will be out for several weeks with a high ankle sprain.

"There's heaps of experienced players who make my job easy and I'm grateful for them," Hopoate said.

"There's heaps of challenges I've faced, the biggest one is probably physicality.

"The boys are much bigger and stronger than me, I'm a lot more sore after the games, I have to use my footwork to get in, get down and get a quick play the ball.

"Good ball defence has been a challenge, when teams are coming at me and I have to make the right decision.

"As fullback, you don't really have to worry about that and that's one of the biggest challenges I've faced so far. I'm still learning and trying to improve every week.

"The first carry of the game sets the tone for me. As soon as I do that, all the nerves are out of my body. That takes me into it."

Supposedly the most laid-back member of his extensive family — Hopoate is one of 11 siblings and his father, John, three of his brothers, Will, Albert and Jamil, and a sister, Pani, have all played first-grade — Hopoate seems well suited to thriving in the cauldron of semifinal football.

He still lives at home with seven of his siblings and does not hesitate when asked about the best advice he has had from the family when it comes to football.

"Don't be scared," Hopoate said.

"My dad told me that one."