I live in Phoenix and keep up with the Cardinals. I don't blame the Cardinals. Sorry but Leonard Davis wanted Left Tackle money for playing guard. The Cardinals knew he was amazing at guard but also knew he couldn't play tackle. The Cowboys and Jerry Jones are more committed to winning as well as having the wealth to afford Davis at guard. However, if the Cowboys started Davis at tackle, they would have problems too.
The Cardinals have been cheap in the past but I don't blame them for not resigning Leonard Davis. You can get quality guards in the draft and their problem hasn't been at guard as much as it's been at tackle.