The Manly Sea Eagles have confirmed second-rower Haumole Olakau'atu will miss between four and six weeks after dislocating his shoulder during Friday night's loss to the Gold Coast Titans.

The injury came midway through the second half, and while Manly were hopeful the damage wouldn't be severe, he will be sidelined for more than a month as he rehabilitates the injury.

While he will avoid surgery, the risk of re-injuring the shoulder will be aggravated upon his return, so the four to six-week return timeline is only a guide, and the Sea Eagles will not rush him back onto the park, instead letting the shoulder strengthen.

It's a horror blow for Anthony Seibold's side, who are already struggling, having lost three of their last four matches.

The losing streak, which has had some asking whether Seibold is safe in his job, has left Manly with a six and eight record in 11th spot on the NRL ladder, although they have a better for and against than any other side in the bottom nine.

Manly turning it around without Olakau'atu will be a challenge, but they are boosted by the fact his time on the sideline starts with a bye this weekend, before back-to-back home games against the Wests Tigers and South Sydney Rabbitohs, and then another bye.

Seibold will be hoping Olakau'atu may be fit in time for the Round 20 clash against the Melbourne Storm, with his side facing a difficult run of games after that against the Canterbury Bulldogs, Sydney Roosters and Canberra Raiders on the road.