Tom Trbojevic has been ruled out for at least a month on the back of a medial tear to his knee, and it has left predictions of the Sea Eagles' demise.

They are hardly unfounded though given their atrocious record without Trbojevic during 2021, and may carry even more concern this time around given an indifferent start to the season with the 2021 Dally M winner on the field.

Josh Aloiai and Lachlan Croker are optimistic that Manly will be able to survive without him however, telling the media the club are prepared.

"Last year we were thrown into the deep end without him, we've experienced it now," Croker said.

"It's not going to be easy ... Oppositions seeing he's not in the team will feel a little bit better. But we have a lot of guys who played a lot of footy last year, they've added another 25 games to where they are now."

The Sea Eagles have stronger options to replace Trbojevic this year too.

Reuben Garrick can slot back to fullback with Tolutau Koula, Christian Tuipulotu or Jorge Taufua sliding onto the wing.

Both Koula and young gun Kaeo Weekes could also show what they can do at fullback.

Whichever one they make, it will be a team effort to replace Trbojevic's output.

SYDNEY, AUSTRALIA - APRIL 25: Kieran Foran of the Sea Eagles celebrates with teammates after scoring a try during the round seven NRL match between the Wests Tigers and the Manly Sea Eagles at Bankwest Stadium, on April 25, 2021, in Sydney, Australia. (Photo by Matt King/Getty Images)

"Whether Foz (Kieran Foran) and Chez (Daly Cherry-Evans) play together on the same side a bit more," Croker said.

"And around the ruck, whoever fills in there is going to have to do something similar to Tom.

"It's a different style (we play now) ... to what we would if he was playing,"

SYDNEY, AUSTRALIA - APRIL 28: Lachlan Croker of the Sea Eagles celebrates scoring a try during the round 7 NRL match between the Manly Warringah Sea Eagles and the Canberra Raiders at Lottoland on April 28, 2019 in Sydney, Australia. (Photo by Matt King/Getty Images)

If Manly can make up for Trbojevic's playmaking, there are still 64 post-contact metres, four tackle-breaks and 207m to replace after his barnstorming man of the match performance against the Raiders during Round 4.

"There's going to have to be times where forwards have to get back earlier to get us out of our own end," Croker said.

Josh Aloiai knows that he and the Eagles' forwards need to get the job done without Trbojevic.

"Obviously we're a little bit gutted about it," prop Josh Aloiai said.

"We know how good he is ... we can't get up here and say it's not a big loss.

"There are 200 or 300 metres there that he gets us going forward so others are going to have to put their hand up."

Manly face the Newcastle Knights, Gold Coast Titans, Cronulla Sharks and South Sydney Rabbitohs over their next four games.