That's a serious question, because I can't tell.  I was at the game today, so there may be some other explanation that's been discussed that I remain unawar of.  But the mid-inning double switch that resulted in Hart jogging from right field to the dugout looked pretty strange.  Hart sat on the opposite end of the bench from Yost after leaving the field, and Yost made a very deliberate trip down to Hart's end where he had a very short, very one-sided conversation with his right fielder before walking away.  Yost's post-game comments on Hart's blunder in the field last night included the following:

"That's his job to know the warning track and the park," he said. "It doesn't matter if the warning track is a mile long or 2 feet long. Especially in your home park, it's your job to know what it is."

Looking at the game situation today, the mid-inning timing of the move itself is hard to figure (at least for me).  Stetter opened the inning and retired Izturis before walkng Schumaker, at which piont Yost pulled Hart in the double switch.  Wainright had already been pulled by the Cards for Thompson, a righty.  Hart had just grounded into a double play the previous half-inning, and like most of the roster, he hits lefties much better than righties.

Stetter's 1st batter was Izturis, so if the intent was simply to do the double switch for offensive purposes alone, the move could have easily been made two batters before.  If the move had a defensive purpose to it, at least partially, it makes no sense to leave Hart in for the first two batters, both lefties who would pull to RF, and then hook him for the right hander. 

That leaves a couple of possibilities (and maybe more I haven't considered):  1) Yost could have intended to let Stetter have the whole inning initially and thus thought he would have the chance to do the double switch after the top of the 6th, but then changed his mind once Stetter put Schumaker on, thus forcing his hand mid-inning if he still wanted the double switch; 2)  Yost either forgot or didn't think of the possibility of a double switch at the top of the inning; 3)Yost wanted to send a message to Hart.

Option 3 would sound completely ridiculous to me if Yost hadn't inexplicably left Hart on the bench for much of late April and May 2007 (blaming a wrist injury that seemed to me to be of mysterious origin, severity and duration).  I'm a Hart fan, and I'm probably a little bit paranoid.  Option 1 seems to be the likely explanation of what happened today.  I didn't see or hear any quotes from Hart after the game, but for what it's worth (and that may not be much), the view through the zoom lens on my camera suggested that Corey didn't much care for being pulled off the field in the top of the 6th inning.  There weren't any thrown gloves or anything, but Hart clearly tried to stay away from Yost and then made no eye contact with him when he approached.

It'll be interesting to see how Ned handles the OF now that Gwynn is back, and even more interesting to see what he'll do when Cameron's available.  My guess is that Hart's starts and ABs will drop a bit as RF will be the most convenient place to get Kapler and/or Gwynn starts.