As much as the NFL Draft is a strategy for teams, it is also a game of chance. Teams can only hope to get the player they planned on, as it all depends on what the teams ahead of them choose to do.
According to NFL.com freakonomics, the NFL Draft is a "game of luck." Teams all want to get the best player for their team but at the same time they want the most valuable. A quarterback like Cam Newton who leads a college team to a national title and also wins a heismen trophy is obviously much more valuable than any other first round pick. However, if a team already has Tom Brady in the starting positions, why would they draft a quarterback? The patriots did not have the first pick in the 2013 draft, but that is to make a point. Teams want the most useful players for their team unless they can get something out of it.
Freakonomics also says that it is much smarter to sell a first round for two second or third rounds. A team can never really know if the player they get will be worth anything come the season. The bears drafted Kevin White in the first round of the draft a couple of years ago. Unfortunately, he appears to have been a total bust for the bears. Also Tom Brady was drafted in the 6th round of the draft! He is arguably the best quarterback ever and was totally underrated going into the draft. I am sure any team would wish they grabbed him earlier. Just shows they can only predict so much, the draft is a gamble.