The Pirates are currently 3.5 games back in the NL Central and still have a chance to catch the Milwaukee Brewers and St. Louis Cardinals. Jose Tabata has been the starting left-fielder for the Pirates, but he is on the disabled list with a strained left quadriceps.
Ludwick presents an upgrade over Alex Presley and Xavier Paul, but probably not enough to make a large dent in the playoff race. However, this does show that the Pirates are at least attempting to stay in the race in the NL Central. Assuming the player to be named later is not a high-impact prospect, this is an okay move for the Pirates. It keeps them afloat in the division and doesn't mortgage their future by giving up a big-time player.