As reported by Jim Salisbury yesterday the Phillies did not extend an invitation to Major League camp to Aaron Nola. This may come as a surprise to some, as Nola was touted as being able to pitch in the Majors immediately or very close to immediately. It was one of the big selling points of Nola prior to the draft. Other picks may end up being better, but none will be better sooner than Nola.
So why not invite him to camp? He wouldn't be competing for a spot, but he could surely learn some and enjoy the experience. Well, what the Phillies want is for Nola to get experience. To work on holding runners (a noted weakness), building consistency in his slider/curve and further developing his changeup. That won't happen in Big League camp. The Phillies have signed a large bullous of back of the rotation options and they have another young starter already on the 40-man to look at (Adam Morgan). If my memory is correct the Phillies will have the stalwarts of Lee and Hamels to go with the pile of Jerome Williams, David Buchanan, Chad Billingsley, Elvis Araujo (on the 40-man, but a lock to likely not make the club), Miguel Alfredo Gonzalez, Aaron Harang, Sean O'Sullivan, Paul Clemens and Kevin Slowey. That's 10 potential Starters for 5 spots.
Nola simply wouldn't get to pitch much. Maybe in the first week or so he'd get in an inning or two in split squad games, but that's not enough to work anything out and it does nothing to start getting him on a pro pitching schedule. Even in SS games, you've got to get all 10 of those guys some innings, plus all of your bullpen options.
In 2014 Nola pitched a big pile of college innings, so the Phillies treated him with kid gloves, limiting his innings and moving some starts around a little. In college Nola pitched every Friday, then rested 6 days. In the minors he was held off the mound for a while to give his arm a rest, then was generally limited to ~5 innings per start, occasionally picking up an extra day or two of rest. In the majors you pitch every 5th day. There's very little variation in that routine and it takes some getting used to. Nola needs to be in minor league camp where he can start getting on that schedule and adjusting his work to fit the routine. Additionally, Nola will be able to get more intensive instruction from a fine staff of instructors and coaches. In the MLB camp, that focus will go to guys likely to make the team.
In the grand scheme of things inviting Nola would be detrimental to his development by leaving him without much work to do. In MiLB camp, he can gets lots of work (likely in Group 3 or 4) and iron out his few rough spots. Besides, he'll be seeing plenty of big league camps in the coming years.