Here is a positional cross section of the analysis users have submitted in their 2014 mock drafts. In short, what is being said per key position. Who are the top 10 at this position and what is being said about them...
The Raiders need a quarterback, but they can get one in the second. They go with Mack, who is the second-best defensive prospect in the draft. He and linebacker Sio Moore would be a force to be reckoned with.
If Barr falls here, the Titans should be elated, they need an outside backer, and the 2nd best backer (third best pass rusher) falls here, but there is a definitive drop off after Barr. I also think Barr is "safer" than Mack based on the difficulty of opponents he played against versus Mack (don't get me wrong, I think Mack still ends up being a stud).
If the Chargers take CB Jason Verrett with their first pick, they could look for a pass-rushing 3-4 OLB with this pick. Attaochu would fit this need. He should be a successful 3-4 OLB in the NFL. He would be a decent value here.