ST KILDA has suffered yet another blow to its fragile defensive depth with Logan Austin to be sent in for surgery later this week on his troublesome left shoulder.

Austin is set to miss an extended period, the length of which is unknown at this stage.

Meanwhile, exciting forward Matthew Parker is in doubt to play as he battles a right ankle concern.

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Parker was hurt in the second quarter of last Sunday's win over Hawthorn but returned and finished the match.

Austin dislocated his shoulder at training last Wednesday, the same injury he suffered in the pre-season.

The 23-year-old also dealt with a groin problem over the summer months and struggled to hit full fitness, meaning he hasn't been in the selection frame despite the club having multiple backline stars sidelined.

Jake Carlisle went in for a back operation in March while Dylan Roberton is sitting out 2019 as he deals with a heart issue.

The Saints signed Jonathon Marsh and Sam Rowe during the supplemental selection period.

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Another of St Kilda's developing defenders, Oscar Clavarino, is listed as being 1-3 weeks away as he recovers from a right ankle syndesmosis sprain.

Austin crossed over from Port Adelaide at the end of 2017 and has lined up in 20 career games.

"It's a frustrating outcome for Logan after doing a lot of work to get himself fit after a groin issue in the pre-season," St Kilda football manager Simon Lethlean said.

"But surgery is the best option to repair the damage to the joint and ultimately set him up for the rest of his career."