Friday, 10 August 2012:

Adelaide forward Kurt Tippett will have to wait at least another week before returning to AFL duties after failing to convince the club he has overcome a bout of concussion.

Tippett, who hasn't played since suffering his third concussion of the season in round 17, was named in the initial Crows squad to take on Fremantle in Saturday's clash at AAMI Stadium.

But the 25-year-old failed to pass a final medical test on Friday, paving the way for former Swan Lewis Johnston to make his Crows debut.

"As the club has stated all along, Kurt will only resume playing once he has been given the all clear by the club doctor," Adelaide football operations manager Phil Harper told the club's website.

"While Kurt has trained extremely well in the past two weeks - and feels 100 per cent well - the club doctor is yet to be convinced that his recovery is fully complete, based on a variety of tests.

"It is expected that his recovery will be complete soon to allow Kurt to resume playing.

"Club doctor Andrew Potter would like to reiterate that all the testing has cleared Kurt of any long-term effects on his health.

"While this may be considered a conservative approach from the outside, the club is determined to continue to put Kurt's health as its prime consideration."

Adelaide will also be without small forward Jason Porplyzia (shoulder), but David Mackay returns from a toe injury.

Fremantle made two changes, recalling defender Alex Silvagni and Nick Suban for Luke McPharlin (suspended) and Dylan Roberton (dropped).

The ninth-placed Dockers enter the match on the back of a five-game winning streak, but their new-found resolve will be put to the test against an Adelaide midfield brimming with talent.

The Crows are ranked No.1 in the league for clearances and contested possessions, and Lyon said it was crucial for Fremantle's on-ball brigade to fight and scrap hard against the likes of Patrick Dangerfield, Scott Thompson, Rory Sloane, Bernie Vince, Richard Douglas and Nathan van Berlo.

"They're a dominating clearance team. They rank in the top four in the AFL in contested ball," Lyon said.

"And from there they like to kick it a lot. They go to their key forwards and they've got a fleet of small players that really damaged us last time."

The Dockers will move into the top-eight with a win over Adelaide, but they'll have to do it against a Crows outfit fighting tooth and nail to secure a coveted top-two spot.

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AAP