Six days to go until the draft, which takes place June 4-6, and we still don't know who's going first overall. Here's my best estimate for the first round as of Tuesday afternoon, as always based on intelligence gleaned from baseball sources about each team's preferences.
At the moment, I don't have a team taking California prep right-hander Lucas Giolito, who missed most of the spring with a minor elbow sprain, but I wouldn't interpret that to mean he won't go in the first round. (I had the Mariners taking him at No. 3 overall in my first mock draft, but I'm now hearing Seattle is no longer interested.) In the next few days, front offices will meet with their respective team doctors to discuss the medical reports of the top prospects, and we'll have a much better sense of where Giolito will go once that process is complete. Until then, I can't predict which team will take him, but he could easily end up in the top 15 picks once his elbow checks out.
Also absent: Lance McCullers Jr., a clear first-round talent who would certainly go in the back half of the first round if it becomes clear that he's signable there. The ripple effect from Giolito moving into the top half of the first round, or any other unexpected player jumping that high, is significant, and we should have a better sense of these possibilities by Friday, which is when my next mock draft comes out.

Houston Astros
Mark Appel, RHP, Stanford
The Astros intend to take whomever they believe is the best player, not the best player for the price, which makes sense given the historical value of the first overall pick. A few days ago I had Appel with a slight edge over Byron Buxton at this pick; today I think it's more or less even.