Manly five-eighth Cade Cust has been ruled out for the remainder of the 2020 NRL season after sustaining a high ankle sprain in Manly's 12-point win over the Bulldogs, per WWOS.

Sea Eagles coach Des Hasler confirmed the news in the post-match press conference on Friday night.

"We've lost Cade Cust for the season," Hasler said. "He's done a high ankle sprain."

Cust will be sidelined alongside fellow five-eights Dylan Walker and Josh Schuster for the rest of the year.

Prop Addin Fonua-Blake was also added to the Sea Eagles injury list on Friday night after a suspected posterior cruciate ligament likely keeping him off the field until round 20.

"Addin's done a PCL in his knee," Hasler added.

"He [also] did it a couple of weeks ago and came back early. We've got a long turn around so he might be chance for next week."