In Spring Training of 2009, the Cardinals took their fourth outfielder, Skip Schumaker, and had him learn second base. The conversion has been considered a success, since Schumaker has been a below average to average second baseman, and, with the exception of a terrible start this year, has maintained his performance at the plate.
Nevertheless, I think the conversion is a major factor in the Cardinals' disappointing year.
Throughout the Tony La Russa era, the Cardinals have employed a series of stopgaps at second base. They won the World Series in 2006 with trading deadline pick-up Ronnie Belliard, who was gone immediately therafter. The 104 game winning National League Champion Cardinals had Tony Womack (and I had to look that up). The next year, they won 100 games with Mark Grudzielanek. Second base has been a position the Cardinals have generally favored flexibility.
The Schumaker conversion changed all that. The organization had invested considerable energy into it. Schumaker himself worked hard to make it work. The Cardinals let Adam Kennedy, an adequate second baseman, go, eating a bunch of his salary. Unless Schumaker turned out to be an embarrassment at second, or stopped hitting, he was going to be out there.
And he wasn't an embarrassment. He was essentially a league-average second baseman. Which was enough for the organization and the fans to consider the conversion a success.
What this also led to is resistance to considering second base an area for improvement. If the Cardinals had simply traded Schumaker the outfielder for a second baseman who performed as Schumaker did, they may have felt differently.
The Cardinals roster is generally not flexible to begin with. Their two best and highest-paid position players occupy the rightmost positions on the defensive spectrum -- first base and left field. Their next best hitter in the first half of this year was in the next slot over, right field. So, the Cardinals couldn't just upgrade their offense by acquiring a "bat" -- it had to be someone who could play a key infield position. Second base is the one position of those where there can be upgrades available, such as the 2006 Belliard acquisition.
But the Cardinals were essentially locked in. Making a change at second base would be tantamount to admitting the conversion didn't work, and there was too much invested in it to do that unless it was blindingly obvious. And so the Cardinals were committed to an average second baseman.