Tom Trbojevic is not the only promising youngster coming through the ranks at Manly.

Outgoing Manly under-20s coach David Heath says he's proud his charges have developed a winning culture under his watch, shooting from 2013 wooden spooners to 2015 grand finalists.

While the Sea Eagles never quite looked like toppling eventual premiers Penrith in Sunday's Holden Cup decider, they were in the contest right up until midway through the second half when the Panthers began to pull away.

Heath won't be at the club next year – he is one of a raft of support staff being moved on by incoming coach Trent Barrett – but said he ends his stint proud of what the young players were able to achieve after buying into his attempts to instil a winning culture.

"Not just on the field but off the field, they've grown into young men and we've developed a winning culture in the club which is good and what the club needs," Heath said after the side's 34-18 loss.

"Obviously not everyone can win but you need a winning culture. There was a point there a few years ago we didn't have it and we got it back."

"There's a number of boys there who were with us last year and that certainly clicked in through last season and as a coach, you want to try and do things and the boys bought into it and we went forward so it was good."

Heath said while it was excellent to have made the Grand Final it was still disappointing not to have gone on with it after giving themselves a chance.

"I thought the second half there were specific points in the game where we could have taken control and we didn't," he said.

"Unfortunately I think in that heat if you make errors within your own half it makes it very difficult to defend and that's what happened.

"I'm trying to push aside the disappointment because I really thought that we could have taken that game and there was a specific point that I thought it was there. We just didn't quite execute where we wanted to. So I'm sort of pushing the disappointment down – I should have pride but I guess it's just the sort of competitive edge you don't want to back that off."

Heath was more tight-lipped on his own departure from the club but said his full-time job as a teacher would keep him busy with coaching off the table for now.

"I don't have anything [lined up in terms of coaching]. The club asked me to move on. They're moving in a different direction and at the moment I don't have anything," he said.

"It's been pretty hectic, so I'm trying to pursue other things."

The Manly Holden Cup side boasts a few possible NRL stars of the future. While fullback Tom Trbojevic is already known to NRL audiences and looks the heir apparent to Brett Stewart's maroon and white No.1 jersey after some scintillating efforts this year, young prop Liam Knight is highly rated at the club and could emerge over the next few seasons while bustling centre Addison Demetriou made the NYC Dally M Team of the Year.

"[Knight] is a forward so he may take a little bit of time in the State Cup but I don't see anything that should hold him back [from an NRL career]," Heath said after Knight's impressive try-scoring effort on Sunday.

"He was one of the best on the field, again he played 80 minutes in the middle – there are not many blokes of that age that can do it. I remember one other player that could and that was Jake Trbojevic so I don't see why not."

Heath said Demetriou would be tested despite his doubtless talent as he joins the full-time NRL squad next year.

"He's going to have to apply himself, he's joining the full-time squad so it will be interesting to see what he does. There's a hell of a lot of hard work ahead of himself," the coach said.