Sorry for piling on, but arm slot aide, the knuckle-curve isn't exactly easy to master -- or others would be throwing it. Off the top of my head, I can only think of two pitchers who have mastered it: Burt Hooton and Mike Mussina. I'm sure I'm overlooking others, but it's not like every team has a pitcher with one in his pitch selection.
I'm hoping both Danks and Crain are healthy enough to open the season with the team. I'm also concerned about Keppinger's shoulder. He's really not in Beckham's league defensively at 2B. If his shoulder isn't healthy enough to allow him to play third, it's a problem.