First, I've been thinking that the acronym BVA (Best Value Available) may be more accurate than BPA, since BPA never truly refers to best player anyway. It is always a combination of player ability, positional value and need. If this weren't the case, none of the QB prospects in this draft would even be considered for a first round pick.
Second, the weakness of most Mock Drafts is that they focus too highly on team needs. Most NFL GMs draft according to some form of BVA/BPA. However, most Mock Drafts, by both the "experts" and the amateurs, look not only at team needs, but at the needs that are the most spectacular, such as wide receivers, pass rushers, etc. No doubt that they can be fun, but this is why they tend to be inaccurate.
Now to look at the Packer's Draft. I'm trying to think of how Ted Thompson might approach this draft. First, there are some "number" needs. The Packers lost 3 interior, run-stopping defensive linemen from last year (C.J. Wilson, Johnny Jolly and Ryan Pickett). We also lost a safety (M.D. Jennings) and 2 offensive linemen (EDS and Marshall Newhouse). In addition the injury history of Derek Sherrod and Bryan Bulaga probably concerns TT and the future of the offensive line.
There is a lot of talk that the Packers have a need at inside linebacker and tight end, but these needs are for upgrades at the position, while the needs at safety, defensive line and offensive line are needs to field a full complement of competitive NFL-ready players. When you also consider Thompson's history in the draft in which he tends to pick "big men" in the first round, I would not be surprised to see the Packers pick Nix, Tuitt, or Hageman.
In any case, we can expect to see the Packers select probably two DL and, at least, one OL in this draft. I'd expect TT to draft a couple of defensive backs, at least one linebacker, a wide receiver, a tight end and maybe a QB if he doesn't draft more than one OL or LB.
Frequently, a guy tumbles down the order on draft day because a team or two that might have drafted him decided to reach for a QB, or the GM fell in love with another player, etc. I imagine TT is going to be hoping for that to happen. Some possibilities that Thompson would jump at to draft if they fell to #21 would be Clinton-Dix, Mosley, Mack and Donald. Other more likely possibilities are Dennard, Gilbert or Shazier, but I think that TT would take Nix before any of them, if he is around. And I feel fairly certain that a certain hot spot will freeze over before Thompson drafts a TE in the first round.