Melbourne could be without star on-baller Clayton Oliver for up to a month after he injured a hamstring in Friday night's AFL loss to Port Adelaide.

While Oliver played out the game, scans taken on the weekend are expected to confirm the Brownlow Medal contender will be sidelined for several weeks.

The Demons have a big month ahead, with games against resurgent Fremantle, then Carlton, then the King's Birthday clash against Collingwood before taking on Geelong.

Oliver is fifth in the coaches' association voting and is a proven Brownlow poller, finishing equal-fourth last year, third in 2021 and equal-10th in 2020.

The gun midfielder has missed only one game through injury in the past six seasons.

The 2021 premiership player is one of Melbourne's biggest stars, winning their best and fairest award four times as well as three All-Australian selections.

Also on the weekend, in-form Western Bulldogs defender Jason Johannisen suffered a serious hamstring injury that could sideline him for up to two months.

St Kilda's win over GWS on Sunday was marred by a heavy head knock for Mitch Owens, with play held up for five minutes as he was helped from the field.

West Coast's brutal injury toll worsened further in Sunday's 116-point humiliation against Hawthorn, with Liam Duggan (neck), Oscar Allen (knee) and Jamaine Jones (ankle) all hurt.