PORT Adelaide forward Angus Monfries will be sidelined for three weeks with a hamstring injury in another setback for his return to the AFL.

Having served a 12-month anti-doping suspension last season as part of the Essendon supplements saga, Monfries was making his way back to full fitness after recovering from a shoulder injury sustained late last year.

But the Power announced on Monday that the 30-year-old suffered a hamstring strain at training last week to stall his comeback plans.

Monfries has played 210 games since making his debut with the Bombers in 2005.

He is the only serious injury concern for the Power, with defender Jasper Pittard (hamstring) and second-year ruckman Dougal Howard (knee) to be assessed this week.

Pittard could come straight into the Power's side for Saturday night's top of the table Showdown with Adelaide at Adelaide Oval.

Howard has made a quicker than expected recovery from a torn ACL.

“They have a few last checks to go, but all things going to plan they should get through this week,” the Power's head of high performance Darren Burgess told portadelaidefc.com.au.

“It’s a really positive bit of news, particularly for (Howard) who’s been out of action with that ACL.”

Half-back Hamish Hartlett will be available for the Showdown after he was a late scratching from Sunday's big win over Fremantle through illness.