ST KILDA young gun Mattaes Phillipou is set to be sidelined for the next few weeks after re-aggravating a plantaris tendon injury in the minutes before Saturday night's loss to Collingwood.

The 2022 pick No.10 was removed from the starting line-up and replaced by Ryan Byrnes just before the opening bounce, after feeling sharp pain at the back of his calf in the final warm-up at Marvel Stadium.

Scans on Sunday ruled out calf tendon damage or anything related to his Achilles, but Phillipou won't travel to Western Australia to face Fremantle this weekend and isn't expected to return until mid-July.

Phillipou experienced issues with his plantaris tendon ahead of the trip to Alice Springs and then sustained a full rupture in the opening minutes of the win over Melbourne at TIO Traeger Park.

The 20-year-old then missed the loss to the Western Bulldogs in round 14 following the bye, before training fully last week to be cleared to return.

Phillipou had also missed the first two months of the season after suffering a stress fracture in his femur in January, which sidelined him until May.

The South Australian returned against Carlton in round nine and has only played three full games this year, including a 23-disposal outing against Gold Coast in round 11.

St Kilda is confident Phillipou will still be able to salvage a block of games in the second half of the year, but an interrupted pre-season has contributed to this run of soft tissue issues.

The Saints unveiled its latest top ten pick Alix Tauru against Collingwood, with five of the club's past six first-round selections – Nasiah Wanganeen-Milera, Darcy Wilson, Tobie Travaglia and Phillipou – playing on Saturday night.

St Kilda is now 5-9 after round 15, sitting 15th on the ladder with nine games to play.