Souths could be left with as much as $4 million in dead salary cap weight over the next four years should Sam Burgess be forced to retire due to a chronic shoulder injury.

Burgess was on Wednesday ruled out of the upcoming Great Britain Lions tour of New Zealand and Papua New Guinea as he nurses a chronic shoulder complaint which hampered his season at Souths.

The playing future of Souths captain Sam Burgess is shrouded in uncertainty. Credit:AAP

The injury has now reached the point where there is a question mark over his immediate playing future.

While Rabbitohs officials remain hopeful their captain will play on in 2020, the club has accepted Burgess will almost certainly be forced to retire before the end of his current contract, which expires in 2023.