Contrast the A's lineup to that of the Angels, where 98.agazillion% of their payroll is tied up in their 3-4 hitters, or to that of the current Yankees, where the opposition's plan is, "Don't let Cano beat us and we're fine." The A's have built their team to have a lot of "pretty good players" without any obvious stars but also without any black holes.
What this means is that if the A's want to upgrade a position, it will likely be a "minor to moderate" upgrade rather than a quantum leap. Yes, you can improve the bat at 2B, but then you also have to sit Eric Sogard who is playing very decently on both sides of the ball. You can get better, but not that much better.
And here's the problem, come trading deadline. The value you have to give up in order to get a better player is the value of the player -- not "how much of an upgrade it is for you". In other words, Alex Rios' value is the same whether you are seeking to replace David Murphy or Nate McClouth. It's why the Rangers might be kicking the tires on Rios, but the Orioles aren't.
For the A's to add a position player to their lineup, they would have to give up the value associated with a really good position player while making only a moderate upgrade and while subtracting a decent player from the mix. Really the same is true of the starting rotation, where to acquire Jake Peavy the A's would be upgrading from Tommy Milone or A.J. Griffin or Dan Straily, all of whom are a lot better than most teams' #5 SPs, and would have to drop one from the rotation. Is it an upgrade? Yes. Does it make the team better? Yes. Is it as big an upgrade as it would be for most teams replacing their #5 SP with Peavy? No. Will the A's get a discount, in trade talks, because of this? No.
That is not to say the A's can't, or won't, find a trade partner for a win-win deal. The one area where a major upgrade might be possible is at SS, where by adding a good player you get the double-whammy of moving Jed Lowrie to 2B where he is far better suited. That's why I've been more keen on a good SS than on a good 2Bman, but it's hard to identify a SS who is good enough to get but not so good as to be off-limits.
Other than Chase Utley, who is good enough, and who as a rental may be cheap enough, I'm just skeptical as to whether a player is out there who represents a big enough upgrade on a team whose strengths include a remarkable lack of "black hole syndrome". Oakland's 3-4-5 isn't the best in the league, but its 7-8-9 often is.
It's why I'll be satisfied if Oakland stands pat at the deadline, armed with a team capable of winning 95 games, with Brett Anderson on the way back to strengthen the front of the rotation. Moderate upgrades at the cost of what a bigger one would be worth? I think I'll pass.