Over the two seasons Bob Geren has served as A's manager, I have actually come to conclude that by and large he really has the right ideas both on the macro ("general philosophies") and micro ("tactitian") levels.
Fans, of course, will always remember the blunders. I didn't like the anointing of Alan Embree as "the 8th inning guy" early in the 2008 season, because Embree was better against lefties, able to go more than one inning, and not that "lights out" overall - and so I was screaming "FIRE GAREN NOW!!!111" when he let Embree serve up a booming double to Vernon Wells and then a mammoth game-tying HR to Frank Thomas, when pretty much any other reliever would have been a better choice for that particular inning. But you know what? If you manage 162 games, you will make some mistakes. The question is how many do you make, and do you general have the right idea? And overall, I think Geren has a pretty keen sense of how to manage a baseball team.
The biggest weaknesses I have seen in the A's game, Geren has noted and addressed publicly. Two years ago, he said the A's needed to run more to keep teams honest and create a better balance to the offensive attack, and that they needed to be more opportunistic about going first-to-third. Geren backed it up by with 2007-08 teams that chose more spots to add the running game to their toolbox, not a bad idea when your offense lacks a lot of good hitters or much power.
In 2008, Geren focused on the team's two-strike approach and has continued the refrain into the 2009 Cactus League season: He wants to see better two-strike approaches from his hitters. Now a good way to improve your team's two-strike approach is to replace Jack Hannahan and Emil Brown with Eric Chavez and Matt Holliday, and a bad way is to tell Jack Cust he needs to start slapping the ball when he's behind in the count. But Geren is referring to neither phenomenon. He's talking about "being intentional" - taking a look at who the hitter is and what the situation is, and if you're Daric Barton and putting the ball in play is of premium importance in a given at-bat, your style and the situation demand that you be better at protecting the plate than at staring down the umpire. Geren's point, I believe, is, "Know who you are as a hitter and know what the situation is, and make your at-bat reflect both." I couldn't agree more that this is an area the returning players can, and need to, improve upon, and Geren is on it.
As far as pitching is concerned - when to remove a starter and which reliever to go to when - I think pretty every team's fans widely believe their manager uniquely has no clue. In fact, it's generally a good idea to try to get at least 5 innings out of your starter if you possibly can, and the bullpen game is often one of "two good choices" or "two bad choices," i.e., more often than not a pitcher makes a manager look better or worse than he actually is based on how he performs. Geren is open to being flexible, not running a given closer out there "just cuz" and occasionally surprising with a 3-inning stint from Ziegler or playing the "hot hand" for a couple hitters, but he's also wise enough not to draw undue attention to himself by constantly reinventing "The Book."
In summary, when it comes to strategy it's natural to think, and usually pretty easy to "prove," that your team's manager is strategically impaired. In fact, I've seen way more to like about Geren than I've seen to criticize and I expect that if he's given a healthy team for a change, far from being part of the problem he'll be a part of what allows the A's to compete for the AL West crown.