I like to think there are two-levels of "worst-case" and "best-case". One is the literal interpretation of the phrase picking out the absolute worst thing that could happen. The other is the reasonable interpretation picking out the worst thing that has some potential of happening that is not close to zero.
For Giolito the "literal worst-case" in the baseball sense is something like he gets injured before this season and never pitches again. Ok, that has a potential that is probably not close to zero, but it's also something that hangs over the head of every athlete in every sport. It's kind of unnecessary to say it because we all know that this threat exists. We have to take injuries out of these worst-case potentialities, because they'd dominate them and make them boring. If we do that, I'd say "literal worst-case" become Giolito struggles in AA and AAA (and majors probably - guys with this talent you move up just to see) to the point where the Nats have to shift him to relief. Where he also fails. Again this is something that I'm putting out there saying that the chance of it happening is very close to zero. An ignorable thought-exercise, not a scouting report .
The "reasonable worst-case" is probably just slightly grimmer than the "fair" pessimist take I put out yesterday. He stumbles a bit in AA and AAA but gets to the majors in 2017 at some point. Spends several years as a mid-back rotation guy because of some combination of finding his level and being consistent. Good, helpful, but not something to build a team around. This sounds bad, but we're setting a worst-case scenario as "Nats have a cheap rotation pitcher for 4-5 years"
The "reasonable best-case" is really nice, in my opinion. It would put Giolito in the rotation at some point this season, doing well but not dominant (think Ross last year), and have him graduating to a full spot next year with a "only if someone better comes along" ROY worthy season. After that the sky is the limit.
(The "literal best-case"? He wins a spot in the rotation in Spring and begins a HOF career with a dominant 2016. Also, the kid can hit!)
I fall closer to reasonable best-case than reasonable worst-case. I see him up this year (late unless injuries force the Nats' hand). Where in relief he shines, much like David Price in 2008. He pitches in the rotation next year and is good to very good and is definitely in the ROY discussion (though it's not an obvious thing). Then he progresses nicely forming into #1 type pitcher by 2019 at the latest. That would be where I am.
Why am I here? Well I feel the Nats have a pretty good rotation so they don't have a strong impetus to push Giolito. They also won't want him to bounce up and down between minors and majors. You also have to consider his service time clock, which they probably won't want to start early this year, kicking arbitration and free agency a year closer. So it would take at least one and possibly two long-term injuries (plus Giolito starting strong) to get him up before September.
Every pundit agrees his stuff is great, so I have a hard time seeing him really struggle for long in the majors. I also understand that even the best pitchers have a year or two of adjustment. Those guys I talked about yesterday? Kershaw's Year 1 was blah. Bumgarner's Year 1 was very good but was followed by two ones that were just ok. Felix's first year was great, but his second year was average at best. Greinke's Year 1 was good/very good but then he had mental health issues and needed a year and a half to get back to the majors. He didn't come into his own until his 6th year. So thinking Giolito will come in and dominate immediately, to me is going a step too far. However the Nats are cautious and worked Strasburg well so I think the time they've taken with Giolito will help with some of these issues adapting to the major leagues. So I give him a first year that may not be as good as it could be but I also don't give him any regression. We'll see.
That's what I think will happen. What would I do? Throw him in the deep end. It'll probably end up with a start like these guys; some great, some meh, for the first 2-3 years. But there's potential there for the quick adjustment. Kershaw's 2nd year was close to great and he hasn't looked back. I want to be sure he is providing Nats with elite level pitching as soon as possible. I want to maximize the BRYCE/Giolito ace time as much as possible and I think that's the way to do it. Of course, the Nats presumably know more than me about what Giolito needs.
Let's get this season started