ST KILDA has committed to handing a list spot to ex-Adelaide listed ruckman Paul Hunter as it takes stock on its talls following Rowan Marshall's foot injury.

Hunter was impressive in the Saints' intraclub on Thursday playing for the 'A' side with Marshall and other ruckmen Paddy Ryder and Shaun McKernan sidelined.

It was a performance that sealed Hunter's future at the club, the Saints deciding on Friday to extend the 200cm big man's two-week train-on stint into a permanent stay for 2021.

Scans on Wednesday revealed a hotspot in Marshall's foot that will rule him out for the season opener against Greater Western Sydney.

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While the 25-year-old will be off legs for 3-4 weeks, coach Brett Ratten told on Thursday the club was still hopeful to see the No.1 ruck on the park in the early rounds of the season.

Rested on Thursday, Ryder is expected to feature in upcoming practice matches against North Melbourne and Carlton and be cherry ripe to tackle the Giants.

Paddy Ryder takes a break during a St Kilda training session at RSEA Park on February 12, 2021. Picture: Dylan Burns

McKernan will also put his hand up for the pre-seasn hitouts after being nursed through training this week while still carrying fluid in a rolled ankle.

With quarters extending back to full-length this season, the Saints are likely to require another ruck option to assist the 32-year-old Ryder.

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Ratten raised swingman Josh Battle as another potential option to pinch-hit in the ruck in the early rounds of the season.

Category B rookie Sam Alabakis, who played for the 'B' team in Thursday's session, is the Saints' other genuine ruck option.

Hunter joins the Saints as his second AFL club following a four-year stay – without an AFL debut – at the Crows that ended following the 2019 season.

The 28-year-old signed at Williamstown for the 2020 VFL season before it was called off due to COVID-19. He then made the dash to sign for South Adelaide and made an immediate impact to be named in the SANFL Team of the Year.

South Adelaide has been hit with a series of other last-minute departures to AFL clubs in recent years with Keegan Brooksby (West Coast and Hawthorn), Hayden McLean (Sydney) and Michael Knoll (Sydney) all being snapped up outside drafts.

Hunter joins under the Pre-Season Supplemental Selection Period (SSP) rules which also saw the Saints sign Mason Wood earlier this month

The Saints have one list spot remaining which could extend to two should defender Dylan Roberton, who is currently weighing up his future, opt to retire.

The SSP closes on March 9 with any list opening able to also be used in the Mid-Season Rookie draft scheduled for June.