Re: 7/20/12 - Reds vs Brewers
I don't think there's much difference defensively between Ludwick and Heisey in LF. Sure, Heisey is the better defensive OF overall, but that's because he can play CF. Ludwick is very fundamentally sound in LF.
The double switch was made last night to move the pitcher's spot in the batting order back. Any improvement defensively in LF, however slight, was incidental. Remember, Ludwick came in for Heisey as part of a double switch in Thursday's game.