The South Sydney Rabbitohs have confirmed winger Alex Johnston has suffered damage to his ribs, but can't set a return timeline.

Johnston's return to the NRL after last season's devastating Achilles injury was cut short on Thursday night.

In the act of scoring his first try of the year, Johnston stayed down in the aftermath, seemingly clutching at a shoulder after landing awkwardly.

He played through until halftime but never looked himself before being substituted out of the game by head coach Wayne Bennett.

It has now been confirmed by the Rabbitohs that he has an upper rib injury, but the club couldn't put a return timeline on the winger, instead labelling him a week to week proposition.

"Alex Johnston has sustained an upper rib injury from our round four game against the Penrith Panthers. AJ is a week-to-week proposition and is working with the Rabbitohs medical team to return to the field as soon as possible," the club wrote on X (formerly known as Twitter).

The fact the club can't put a return timeline on the winger would indicate that there is no serious damage that has been substained, and it could well be down to a pain management and tolerance decision on Johnson's part as to when he can return.

The winger, who missed time at the end of last year and start of this year owing to his achilles injury, will be desperate to get back on the field and continue his pursuit of the all-time try-scoring record held by Ken Irvine.

Thursday night's try means he needs just 17 to break the record, now sitting with 196 to his name.

The winger is also off-contract at the end of the current season.