Players pretty seldom arrive at the big leagues fully formed. Plouffe couldn't very well, and was not near the hitter he is, Dozier couldn't hit and couldn't really play short. Gibson had a poor beginning at the big league level, May began brutally. Perkins, too. Anyone remember Hunter's first pass at the majors? Banjo-hitting, sent back to AAA, then came back better, but still slugged .380 on the year. It takes time -- development doesn't stop at AA or AAA. If the bar a prospect needs to meet is: from day one, being an average or above major leaguer -- displaying competence across the board, then the list is pretty short. Mauer. Liriano. Maybe a few others. The bar can't be that high. I have great respect for the value of an average MLB player, and I don't object to trading prospects to fill a slot or two when it can make a big difference. Average (not replacement level -- average) is good. Probably a WAR of 2 or so. And over the course of a season, having a bunch of such players is very valuable. Right now, for this season, such a player is worth 1.0 WAR, or less. I don't want to give away a player with a 50/50 chance of being an MLB regular for that. To get average MLBers in bulk at an affordable price, you grow them in your farm system.