ADELAIDE forward Chris Knights and Port Adelaide veteran Warren Tredrea agree there'll be a distinct lack of 'Showdown spirit' when their sides meet at AAMI Stadium on Saturday afternoon.

Games between the cross-town rivals were a regular feature of the pre-season calendar last decade, until the clubs sought to preserve the status of the home and away encounters by petitioning the AFL against playing summer Showdowns.

Tredrea said he understood the benefits of scheduling a home game for both sides in the first round of the NAB Cup, but admitted to being disappointed by the fixture.

"I don't think it (Saturday's game) is a Showdown. It's a pre-season match against Adelaide our arch-rivals, so there might be a little bit more in it than any other pre-season game … but if we were playing Hawthorn or Richmond the focus would be exactly the same," Tredrea said on Thursday.

"Both clubs have worked pretty hard to build this game (the Showdown) up. It lost a little bit of its focus a few years back, but the last three real Showdowns have been cracking games."

Knights shared Tredrea's sentiment, but said the Crows were still looking forward to kicking off their 2010 campaign against the Power.

"They (pre-season Showdowns) don't hold as much prestige as they do in the premiership season, but I don’t mind playing Port Adelaide in a practice match," Knights said.

"It probably doesn't have as much weighting or emotion, but it's still good to play Port Adelaide. I think it's a good opportunity to play a local game in front of our local supporters here in Adelaide."

The Crows will be without six first-choice players, including Nathan Bock (calf), Jason Porplyzia (pelvis), Scott Thompson (knee), Nathan van Berlo (back), Brad Symes (whooping cough/knee) and Brad Moran (knee) for the twilight clash, meaning a number of young players will be given an opportunity.

Phil Davis, Rory Sloane, Tony Armstrong, Shaun McKernan, Myke Cook, Jared Petrenko, Taylor Walker, Jarrhan Jacky and rookie Chris Schmidt have all been included in the 29-man squad.

This weekend's round of NAB Cup games will also be the first test of the competition's four new trial rules.

Boundary umpires will be able to award free kicks, while players can determine whether to play on after receiving one.

The Crows have had an umpire at most of their training sessions this summer and Knights said the play on/advantage rule had caused the most angst among players.

"The only problem is that the umpires have to make sure they're really quick at determining whether or not it's play on," he said.

"We've found at training that if the umpire is too slow and the player predicts [the play on call] before the umpire, it results in a 50m penalty - which is within the rules but it's one of those grey areas.

"It gives a player the chance to take the advantage that he might not have had before. If you play on in the forward line and kick a point it might be a bit detrimental to the team, but it's one that will keep the game nice and fast."

Chris Knights is a $372,000 forward in this year's Toyota AFL Dream Team.

Warren Tredrea is a $336,200 forward.