How much if it is personnel and how much is coaching?

[*ochocincos*]

Playcalling is a huge factor. Deciding whether to send a guy to rush the passer or drop back in coverage, stick to a receiver or stay in a zone, what particular route you're running or whether you're running inside vs outside, etc.

From what I saw (I didn't watch every single game, but I watched a majority), the playcalling could get more creative to utilize the skill set of the players better.

With that said, I do feel like some (most?) players have clear weaknesses such that they could be upgraded if they can find a better player.