A year ago, trading a prospect named Starling Marte for a veteran might have made sense for the Pittsburgh Pirates. But he's really no longer a prospect after being called up recently, and he is under club control until 2018.
The same was not true of someone like the now former Philadelphia Phillies outfielder Hunter Pence, who is signed only until the end of 2013 and was traded to San Fransisco on Tuesday. He currently has a .271 average, a .336 OBP, and a slugging percentage just below .500. And if the Pirates had continued to pursue Pence, the Phillies would have wanted both Marte and Brad Lincoln, meaning that the Pirates would have given up their chance to trade for Travis Snider.
The Cleveland Indian's Shin Soo Choo is another player that supposedly would have commanded Marte in trade. Choo is a bit better than Pence, and is currently sporting a .288 batting average, a .376 OBP, and a slugging percentage also just below .500.
Based on his stellar rise through the minor leagues, Marte projects to be better than both Pence and Choo. Meaning that a straight-up trade of Marte for one of the aforementioned players would have meant a sacrifice of several years of production just to help the Pirates in 2012 and 2013.
Perhaps an even better player than the other two would have been the Minnesota Twins' Josh Willingham. He actually represents the player that Marte might grow into someday, and he is signed until 2014.
Straight up, Marte for Willingham might have been a good deal for the Pirates. But Willingham would have commanded at least Brad Lincoln as well, which means that the Bucs would effectively have given up Marte and Snider for him.
There is a small chance that Marte will be a bust, or at least a disappointment, and in fact, he does appear to be having some "teething" problems in 2012. There is a much larger chance that he will become as good as, or better than, the people he might have been traded for, perhaps as early as 2013—in which case, trading him would have been stupid.
Everyone knows what Pence and Choo can do. Based on his minor league experience, we can only guess what Marte can do. But sacrificing his long-term, if speculative, potential for one or two years of greater certainty didn't make sense.
As Warren Buffett would say, "You pay a very high price [in the marketplace] for a cheery consensus."