ST KILDA will this week weigh up the immediate playing future of forward Paddy McCartin after the 2014 No.1 draft pick was left concussed for the third time this season – and fifth time in the past two years.

The 20-year-old suffered his latest concussion after colliding into teammate Tim Membrey in a marking contest during the first term against Gold Coast.

McCartin was put through, but failed, the usual 20-minute assessment and took no further part in the match.

The Saints last month ruled out Billy Longer for at least four weeks after the ruckman experienced delayed concussion symptoms from a head knock he received in the VFL in May.

Carlton defender Ciaran Byrne will miss the next 12 months after scans confirmed the Irishman ruptured the anterior cruciate ligament in his right knee against Collingwood.

The 21-year-old was bumped by Magpie Travis Varcoe after a clearing kick from defence in the last quarter, which forced the Blue to land awkwardly.

Byrne, who played 11 games this season, was visibly upset as he was taken off the ground on a mobile stretcher.

Gold Coast midfielder Matt Rosa, who missed three weeks earlier this season with a left hamstring strain, suffered a right hamstring injury against the Saints and did not feature after quarter-time.

Essendon is likely to enter Sunday's clash against St Kilda without its two leading ruckmen following injuries to experienced pair Matthew Leuenberger and Mark Jamar against West Coast.

Jamar injured his left hamstring in the third quarter and sat out the rest of the match with ice strapped around his affected leg, while Leuenberger had his left knee assessed just minutes later at the interchange area.

Leuenberger managed to return to the field and battled through soreness, but his night ended midway through the last quarter because of the knee issue.

Port Adelaide key defender Jack Hombsch, who was on the verge of returning after missing the past three matches with a hamstring strain, is facing another spell on the sidelines, this time with a quad injury.

The 23-year-old picked up his latest setback while performing a short 10-15m kick during the Power's indoor training session on Thursday.

"He's got a quad strain probably; he's got quad soreness at the moment," Power coach Ken Hinkley said after his side's win over Richmond on Friday night.

"We've had scans (and) it doesn't look like it's going to be a short-term injury."

Blues defender Jacob Weitering, the No.1 selection in last year's NAB AFL Draft, rolled his left ankle in the third quarter against Collingwood but managed to play out the game.