I'm practically apoplectic at where this set of four mocks has Skal.  Skal has worse college stats than Chriss, Davis, and Ellenson.  He doesn't rebound.  He doesn't shoot from long-range.  He blocks shots sometimes, but fouls at an alarming rate -- one every five minutes.  He was a complete disappointment in his one season in college.  He was also very old for a freshman.  He turned 20 in March.  That's the age of a sophomore, not a freshman.  He's 9 months older than Davis, 10 months older than Elenson, and 16 months older than Chriss.  
He doesn't have good reach for a big.  He's pretty lightweight.  His athleticism isn't special (31 inch vertical as a 19 year-old). He's someone who looked good playing kids 2 years younger than him on the AAU circuit a couple of years ago, but has very limited basketball skills.  That he is between 4-9 in all of these mocks is ludicrous.  (Heck, that he's #11 in draft express' mock also makes no sense).  He doesn't resemble an NBA-ready player, and at age 20, it's very difficult to see the upside. 
I will be very annoyed if the Celtics pick him in the first round, and I will openly mock any team that picks him in the top 20.  Players who turn 21 during their rookie season should not be expected to spend time in the D-league if they're lottery picks.  
He's tall, but not exceptionally so for an NBA big.  That's it.
/rant