Tom Trbojevic scores in the corner for Manly against the Panthers on Sunday.

While Manly coach Trent Barrett is happy with the effort shown by his players, he has unloaded on what he says is a costly inability to stay in games for the full 80 minutes.

Barrett added that while there is a huge amount of experience and salary cap currently sitting on the sidelines for Manly they should have been able to close out a win against Penrith from 24-4 ahead on Sunday afternoon at home.

"I am [angry] because we were the better side again for an hour. And not just by a small margin, at 24-4 that should be enough to put a team away and it wasn't and that's the disappointing thing," Barrett said after his team's 31-24 loss.

"They worked so hard to put themselves in that position and threw it away. That's the disappointing thing. That was a massive game in terms of our season and now it's going to be real hard [to make the finals]."

Barrett said it has been a recurring theme of Manly's season and until they can rectify it he will continue to be sitting in post-match press conferences analysing losses.

"The players are sick of it, I know they are, I know they're trying but until we learn to do it we're going to be sitting here again," he said.

"We've got a lot of players out of position, we've got inexperienced halves, we've got some young players in there who aren't used to dealing with the kind of adversity we're in at the moment and I get that and I understand that and the way they've handled themselves off the field is a credit to them, the players.

"I'll never question their effort and their commitment to what we're doing because they work bloody hard all week and that's what [annoys] me the most is that we put ourselves in a position to win on the back of how hard they worked and throw it away as easily as what we've done.

"It was the same in Canberra last week – a try before half-time and then two tries straight after half-time and there's a 15-minute period where we lost the game again and we did it again tonight."

He said while there is no shortage of effort from the players at training, to win at NRL level you have to hang in for 80 minutes.

He added that despite having $3.5 million dollars worth of salary cap out injured in the shape of players like Daly Cherry-Evans, Jamie Lyon, Steve Matai, Brenton Lawrence and Feleti Mateo the team should still have been able to win with such a big lead.

Asked if Manly's notorious mental toughness – that saw them regularly play better the more adversity they faced over a run of 10 straight finals appearances from 2005 to 2014 – was disappearing, Barrett also referred to the amount of experience that had departed the club prior to his tenure to go with the current injury toll.

"I don't think it's disappearing. You look at the personnel, that's what's disappearing and I think that's pretty obvious.

"You take out your captain, you take out Matai, you take out your halfback, you take out Lawrence. You take all them out and from the last few years you take out [Kieran] Foran, you take out [Anthony] Watmough, you take out [Brent] Kite, you take out [Jason] King, that's a lot of experience to lose and you go through our side at the moment and we are down on experience and it's going to show in some stage and it's showing now in a 15-minute periods in our games and the only way you can fix it is to play games.

"They won't give up. We'll turn up again next week against the Titans and front up again but the fact of the matter is we're missing a hell of a lot of players and we've had a rough trot and nothing's going right. We've just got to hang in and keep going."