ST KILDA ruckman Tom Hickey will miss up to six weeks after suffering a medial ligament injury in his left knee while playing in the VFL on Saturday afternoon.

Hickey left the field in the first half of Sandringham's 14-point win against North Ballarat.

The Saints were relived the 26-year-old wasn't sidelined for longer.

"There were initial fears that he may have damaged the ACL but scans (on Sunday) cleared him of that," football manager Jamie Cox told the club website.

"Tom will begin his rehab immediately and is likely to be sidelined for 4-6 weeks as he recovers from a medial strain.

"While obviously disappointed to be missing a few weeks, at the same time he acknowledges that the prognosis is now much more positive than initially feared."

The Saints face Carlton on Saturday afternoon at Etihad Stadium, with Sydney and the Western Bulldogs to follow, before having a week off with the bye.

Hickey missed the round five game against Geelong, with coach Alan Richardson saying the ruckman had been too sore to play but would have been dropped for poor form, regardless of his fitness.

The former Gold Coast big man played all but the final two matches last season, which he missed with a calf injury. He went on to finish eighth in the Trevor Barker Award.

Incumbent ruckman Billy Longer racked up 48 hit-outs in the Saints' upset Friday night win against Greater Western Sydney in what Richardson described as "probably Billy's best game for our footy club" after the match.

St Kilda sits in eighth spot at 4-3, with hard-hitting forward Mav Weller expected to return from a rolled ankle this week.

Tough onballer David Armitage is recovering from groin surgery while young forward Josh Battle is dealing with bone bruising in his left knee.