Adelaide's expectation of reinforcement by speedy winger David Mackay has been dashed by a tenacious hamstring complaint that again kept him from training on Tuesday.

Mackay will now miss his fourth match with the hamstring problem, again depriving the Crows of a vital cog in their efforts to play with speed and precision through opposition defences.

Already needing to formulate a plan for Lance Franklin that does not feature All-Australian defender Nathan Bock (heel), Adelaide have holes to cover in attack where Patrick Dangerfield is still recovering from a back strain.

"Injuries are never good, the last couple of weeks we've had some tough ones with a couple of key players to our side," said Crows midfielder Nathan van Berlo.

"It does hurt us, we'd love to have Nathan out there this weekend with the forward line Hawthorn have got, but we're confident the guys we've got down back and also the other personnel will be able to shuffle round and get a match-up we think will be suitable for us for Friday night."

For all their physical worries, van Berlo pinpointed mental errors as key to the Crows' loss to Collingwood, saying they had been unable to concentrate for long enough periods to beat a top four side so far.

"We felt that part of the way Collingwood were able to expose us on the weekend was our own fault, obviously them scouting and finding flaws in our systems (was part of it), but the fact is we weren't able to do things at the level we expect of ourselves," he said.

"It's a combination of a lot of things but part of it is concentration, being able to sustain a high level of performance for the whole game.

"It's something we've had some issues with, particularly early this year, we played some really high quality football for short periods of time. We've certainly rectified that I believe and be looking to improve further from here on going in."

As befits a future leader, van Berlo produced some neat rhetoric when considering the Crows' fight to be a genuine contender at the back end of 2009.

"This year there's been a lot of talk that we haven't beaten a top four side ... there's no-one saying we can't do it," he said.

"I think there's a difference between saying we haven't done it and we can't do it, and the confidence in the group is such that we believe our best is good enough to beat any side in the competition and there's no wavering from that."

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