As expected, the experienced front-rower will miss the Wembley showdown with knee ligament damage sustained in Sunday's 40-22 Super League win at Huddersfield.

"Jason won't be available until the play-offs," said coach Daniel Anderson when he named his initial 19-man squad.

That squad includes England's Samoa-born prop Maurie Fa'asavalu, who remains doubtful with a hamstring injury.

"I would be more confident if Maurie had done a training session with us, but he still hasn't trained with the team since the semi-finals," said Anderson, who will not announce his starting line-up until an hour before kick-off.

Former Huddersfield and Warrington prop Nick Fozzard is expected to take Cayless' place, while club captain Paul Sculthorpe, Australian back-rower Chris Flannery and former Wigan prop Bryn Hargreaves will make their Wembley debuts after missing Saints' win over Catalans Dragons a year ago.