What has his performance been like?
After being drafted out of high school in 2010 Nick Castellanos has been pushed aggressively by the Tigers organization. He has responded to the challenge of going from the Gulf Coast League to AAA in less than 3 years with tremendous results. Castellanos has hit above .300 in each year in the minors thus far. In 2011 and 2012 he displayed decent power but nothing that would be overly impressive for an MLB corner-outfielder. He had 7 HR in 2011 and 10 HR in 2012 while getting over 500 AB in each of those seasons. Castellanos even struggled mightily in the AFL this past off-season. This was discouraging and his 31 strikeouts in 99 AFL AB were considered by some to be a red flag. He also hit just .242 there while his BABIP was within an acceptable range, so the batting average was legitimately bad.
What is his current status?
After struggling in the AFL and AA last season, especially with his K:BB numbers, the Tigers aggressively started Castellanos out at AAA this season. He has been extremely impressive thus far. Castellanos' patience at the plate has improved dramatically. After posting a 4.1 BB% and 22.3 K% at AA he now has a 10.8 BB% and 17.7 K% at AAA. His improved patience and approach at the plate has led him to see better pitches and that has resulted in 10 HR and 31 total XBH thus far in just 279 AB. It's quite encouraging that Castellanos has improved in each month so far and is red-hot in June with 4 HR, a .361 BA, and a 1.035 OPS.
What can we expect moving forward?
I think that Castellanos will be an above average fantasy outfielder. He'll likely hit for average with very good power in the 20-25 HR range with upside potential for even more as he continues to develop. Wil Myers gets much more attention but they have each been at AAA in the International League this season and despite Castellanos being almost a year and a half younger than Myers they have respectively put up a similar performances this year. Castellanos is hitting .290 with a .841 OPS while Myers is hitting .286 with a .876 OPS at AAA. Castellanos has a lower K% at AAA while performing similarly in pretty much all the other statistical categories. I think that Castellanos will be called up by the all-star break. With Andy Dirks struggling and Castellanos getting hot at the plate the promotion would make plenty of sense. There's a legitimate chance that Castellanos will out-perform Myers in MLB this year. Please don't get me wrong, I am a big believer in Myers but I am just pointing out that Castellanos can reasonably be valued somewhat similarly to Myers at this point. Myers has also been extremely hot at the plate in June and will likely have a very nice fantasy impact the rest of the way himself.
While Myers is owned already in almost every fantasy league it's Castellanos who can still be invested upon in most single-season leagues. Castellanos wasn't even on Keith Law's recently updated top-25 while Myers was 7th so Castellanos is really not getting enough attention at this point. I recommend giving him the attention he deserves.