Onitoni Large is one of Manly's highest-rated prospects in years but coach Kieran Foran will continue taking a cautious approach with the teenage NRL rookie.

As Tom Trbojevic returns at fullback in Saturday's trip to face Newcastle, Foran has been forced into another shake-up in his spine after half Joey Walsh suffered a season-ending broken jaw.

Clayton Faulalo, who has been deputising for Trbojevic in the No.1 jersey, has shifted to five-eighth, despite never playing the position for the Sea Eagles at NRL or NSW Cup level.

Walsh and Large, who captained the Junior Wallabies and played in the under-19 State of Origin fixture for NSW. are viewed as the club's long-term halves prospects.

Manly's finals hopes hang by a thread against the Knights but Foran is reluctant to throw Large into a side that has lost six games on the bounce.

"We're really excited about the career of Onitoni and he's been in and around the group the last month and a half," Foran said.

"He's been 20th man a few times, so we're really starting to get him closer to the action.

"But at this stage of our season and just where he's at in terms of his development, it's important that we prioritise that and don't throw Onitoni into the fire just yet.

"He's growing each and every week, we're extremely excited about where his future is going."

Foran said he never gave any consideration to easing Trbojevic back in at centre or resting the fullback for the rest of the season after the 2021 Dally M medallist sat out the last month with another hamstring issue.

Trbojevic has only played 11 NRL games this season.

"He's the best fullback at the club and if he's fit and firing, then he plays fullback for us," Foran said.

"It's as plain and simple as that. When he's on the field, we're a better footy team."

Australian Associated Press