I read three different pieces about last week's Marlins-Padres deal -- for example, here and here -- without seeing a single mention of what I consider the primary driving force in the deal: Cameron Maybin's minor-league statistics.
To this point, Maybin has failed his major league trial. He hasn't failed it badly. In 2009, he was decent in his 54 games with the Marlins. In 2010, he was less than decent in his 82 games with the Marlins.
Maybin has 610 plate appearances in the majors, which is equivalent to roughly one full season (with a day off, here and there). His numbers include 172 strikeouts and a .313 on-base percentage, neither of which are really acceptable for a player without a great deal of power.
But that's not really the player the Padres traded for. The Padres traded for the player with (roughly) three full seasons in the minor leagues and a .393 on-base percentage, not to mention a .478 slugging percentage and a significantly lower strikeout rate.
Now, the majors are harder than the minors (one point to the Boy Wonder for obviousness!). But the majors aren't that much harder than Triple-A, and Maybin's Triple-A numbers are fantastic. For a fine defensive center fielder, anyway.
Of course the Padres already have one of those in young(ish) Tony Gwynn. The problem is that Gwynn isn't likely to hit much, ever. He's such a wonderful fielder that you can live with his hitting, but you would rather not.
Maybin might not hit. There are 610 plate appearances suggesting that he won't. But there are nearly three times as many plate appearances -- his time in the minors, and he's still only 23 -- suggesting that he will hit, if given the time.
If Maybin does hit, he'll be more than worth the two relief pitchers the Padres gave up to get him. If he doesn't? You live with a decision that didn't work out. If you're not willing to trade two relievers for a young every-day player with potential, you might as well get out of the baseball business and find a real job.