Grienke I think is a stud and will be this year. He will drop in a draft do to playing for KC and a drop in Wins, but how about getting a solid contribution in ERA, WHIP, and K's from a mid-round pitcher? No he won't be the tops in majors in Wins, but if you can get him in mid-rounds he will really round out a staff and help.
I think greatest potential to blow up into a star is Harden. Huge upside, only problem is he is now the "ace" in Oakland. He has the added pressure plus he'll be matched up against other aces.
On another note, I like Victor Zambrano. I don't think he is a super sleeper, but he might be a late bloomer. He's almost 30 but it isn't like he came up 10 years ago, been in the majors since 2001 and then only threw 50 innings. Zambrano is still learning and can strike out a decent number of batters. Will he put it together this year, or ever? Right, like anyone knows the answer to that question. Will be an interesting mid-late pick as a gamble.
...Boston papers now and then suffer a sharp flurry of arithmetic on this score; indeed, for Williams to have distributed all his hits so they did nobody else any good would constitute a feat of placement unparalleled in the annals of selfishness. -Updike