The Sydney Roosters will head into Sunday afternoon's game against the Manly Sea Eagles without both Joseph Suaalii and Billy Smith after the duo suffered concussions in a head clash at training.

The double blow adds to a long list of injuries for the tri-colours, with all of Angus Crichton (knee), Egan Butcher (HIA), Jake Turpin (ribs), Sitili Tupouniua (neck), Nat Butcher (ankle), Brandon Smith (thumb), Sam Walker (knee), Paul Momirovski (shoulder) and Connor Watson (knee) already unavailable.

Turpin has overcome his injury and is named to start, while Nat Butcher is an outside chance of playing after being named on the reserves list.

Trent Robinson confirmed during his press conference after the club's captain's run on Saturday morning that Suaalii would miss the game, while the club added Smith's name to the absentees shortly after.

"He's out. He got a bit of a knock yesterday. That's a bit disappointing so he will have to wait a couple of weeks," Robinson said when asked about Suaalii's return from a previous injury.

"He just had a [head] clash at training and didn't pull up great from it. It's pretty mild but not enough to get through to the game."

Suaalii had originally been named on the wing for Sunday afternoon's clash against Manly, while Smith was in the centres.

The Roosters have already confirmed that Corey Allan will play in the centres, while Junior Pauga will play his fifth game of the season on the wing vacated by Suaalii.

Jaxson Paulo has been brought into the now 21-man squad as cover, with the team to be cut to 19 players at 4:05 pm (AEST) on Saturday, 24 hours before kick-off at Manly.

Both Suaalii and Smith will only miss one game despite having an 11-day period to return, with the Roosters having a bye next week ahead of Origin 3.