William Zillman was superb in the second half of the Titans' win over Penrith.

Zillman in doubt, Olive on ice for Titans

Titans co-captain William Zillman is in doubt for the Round 1 season opener against the Knights on Sunday but coach Neil Henry insists Rabbitohs recruit John Olive won't be a last-minute inclusion.

Although paperwork is still to be finalised on Olive's move from Redfern to the Gold Coast, Olive joined the Titans' playing group on Monday on day one of a three-year deal and again trained with the squad in driving rain on Tuesday.

While he has been named at fullback Zillman did not train on Tuesday afternoon but will be given until later in the week to prove he is fit to play his first game since Round 10 last season when a chronic back injury ended his 2015 campaign early.

There are seven club debutants in the Titans' 19-man squad with Henry non-committal about Zillman's chances of wearing the No.1 jersey against Newcastle at Cbus Super Stadium.

"'Zilly' is on restricted duties with a bit of a calf problem and we'll wait and see," Henry said.

"With the long turnaround and a couple of days off this week we'll know more about him later in the week so we're just holding off on that at the moment.

"We'll be training with an extended squad through our opposed sessions."

With Josh Hoffman named at left centre David Mead will be the man to move to fullback should Zillman be ruled out but Olive won't be rushed in on the wing.

Although Leva Li has been named on an extended bench, Henry left the door slightly ajar for Olive to make his Titans debut as early as this week.

"It's subject to everything being squared off," Henry said of Olive's possible inclusion. "Both clubs have agreed to it but it's waiting for the NRL to sign off on it as to whether he'd be available to play this weekend.

"At the moment he's not in the picture as playing but time will tell.

"He has made it here pretty quickly and settled in. He knows Brian Kelly through [under-20s] Origin and obviously Chris McQueen and Eddy Pettybourne so there are a couple of familiar faces for him.

"He's an outstanding schoolboy talent, played most of last year with North Sydney in the NSW Cup competition as a young player and a prospect we had agreed to terms for two years anyway and we've got him a year early which is great."

Nathan Davis and Leivaha Pulu are in line to make their NRL debuts against Newcastle with Tyrone Roberts, Ashley Taylor, David Shllington, Zeb Taia and Chris McQueen all to play their first games in Titans colours.