PORT Adelaide defender Jack Hombsch will be sidelined for up to a month with a knee injury.

It's a huge blow for the unbeaten Power heading into the top of the table Showdown against cross-town rivals the Crows at Adelaide Oval on Saturday night.

Hombsch suffered a minor medial ligament strain of his right knee in the late stages of the Power's 89-point win against Fremantle last weekend.

The Power's high performance manager Darren Burgess expected Hombsch to be out for three to four weeks.

"The injury happened in the final few minutes of the game," Burgess told pafc.com.au

"He pulled up a bit sore (on Monday) and scans on Tuesday showed some minor medial damage."

Jasper Pittard (hamstring) will need to pass a fitness test at the club’s main session on Thursday, while Hamish Hartlett (illness) will be available for selection.

Utility Jackson Trengove is likely to fill in for Hombsch.

Trengove has played the majority of his career as in defence, but spent most of last season in the ruck and has trained in the forward line this year.

Youngster Logan Austin will also be in the mix.

The 21-year-old played 11 games last year, but had an interrupted pre-season as he recovered from off-season ankle surgery.

Austin is starting to regain match fitness with the club's SANFL team.

Hombsch, 24, started the season strongly as he looked to make amends for a disappointing campaign last year.

He played the first 10 games in 2016 before he injured his hamstring against Melbourne in Alice Springs.

A quad strain a couple of days out from his comeback game delayed his return before hip surgery prematurely ended his season.

Hombsch is off-contract at the end of the season, but the Sturt product is keen to secure a new deal with the Power.