ADELAIDE ruckman Sam Jacobs is expected to miss at least another week with a knee injury, pitting novice Reilly O'Brien against North Melbourne veteran Todd Goldstein at Marvel Stadium on Saturday night.

In better news for the Crows, winger Paul Seedsman could be back within a month from a knee injury after scans dispelled fears of a torn ACL.

Jacobs missed last Thursday night's loss to Geelong at Adelaide Oval after suffering a knock to his knee in the round two win against Sydney at the SCG.

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Crows assistant coach Ben Hart on Monday said Jacobs was unlikely to be ready to face the Kangaroos.

"He's unlikely at this stage, but we'll have to wait and see," Hart said.

"He got a knock to his knee which was pretty sore last week and we just have to wait and see how that pulls up.

"He did a little bit this morning, but not a great deal, so hopefully just one more (week), but you never know."

O'Brien, 23, was well beaten by Cats big man Rhys Stanley as he filled in for Jacobs, playing his first AFL game since round 21, 2016.

Seedsman arrived at West Lakes on Monday morning on crutches, but in good spirits after scans revealed bone bruising on his knee, rather than the initial thoughts of a season-ending ACL injury.

Hart was hopeful Seedsman would only miss another month of football.

"They have to wait and see because bone bruising is an interesting one as to how long that can take, but 12 months as opposed to a month is good news, so we're happy with that," Hart said.

Meanwhile, unlucky second-year defender Andrew McPherson has had another setback after suffering a hamstring injury in the Crows' SANFL loss to Glenelg last Friday night.

McPherson – who missed most of last season with groin and hamstring injuries – left the ground at the 20-minute mark of the first quarter.