The Sydney Roosters will chase the signature of South Sydney star Alex Johnston and attempt to extend the tenure of their own young gun Latrell Mitchell as part of their contingency planning for the departure of Roger Tuivasa-Sheck.

As revealed by Fairfax Media, Tuivasa-Sheck will join the Warriors next year as a replacement for fullback Sam Tomkins, who has been granted an early release for family reasons. The Roosters had hoped to retain Tuivasa-Sheck but were only able to table him about half of the $800,000 per annum that was on offer across the Tasman.

Roosters chasing Rabbitoh: Sydney Roosters will target South Sydney's Alex Johnston. Credit:Getty Images

The stunning coup could have further ramifications, with the Roosters also likely to be in a position to make an audacious raid on Israel Folau should the code-hopping Wallaby decide to return to the 13-man code, however the Australian Rugby Union believe its flexible contract deal will keep him in rugby.

Johnston is off contract at the end of the season and would like to remain with the premiers. But while he is keen to make the transition from the wing to fullback, he won't get a chance to wear the No.1 jersey while Greg Inglis is at the Rabbitohs. Complicating the issue further is the fact that Inglis, despite being contracted until the end of 2017, is being pursued by cashed-up European rugby franchises.