NFL free agency takes on another unique turn in 2011. As a result of some weird legal mumbo-jumbo any free agent that is signed to a contract will not be able to practice with his team until August 4th. Apparently that is the date of the new league year, and that is also the date which all teams have to be under the cap.
This does not apply to rookies or undrafted rookies, but it does apply to any free agents that re-sign with their club, and any players acquired via trade. So say the Raiders sign Zach Miller on Friday, he can't hit the practice field until August 4th.
This will effect the Raiders the most on the offensive line. They only have Veldheer, Campbell, Loper and Carlisle currently under contract, and there is a good chance that Carlisle will be cut. The Raiders should be able to get deals inked with their rookie Wisniewski and Barksdale well before August 4th, but there is no doubt that the Raiders are going to be scrambling to get any cohesion on the offensive line. Especially for the first preseason game which is on August 11th.
It could be much worse. Any team looking to add a starting QB via free agency or trade is stuck in the Wild West without a gunslinger.