Even moreso than Gerrit Cole, Jameson Taillon's minor league career has kind of vexed prospect guys. Everybody that watches Taillon throw in person reports back that he's got borderline-elite stuff. You can check out the piece Kiley McDaniel did for FanGraphs last summer, when he slotted Taillon just behind Dylan Bundy as a prospect, said he has a "non-zero" chance of becoming an ace and that even if he doesn't (noting that there are never more than 15 or so pitchers in baseball that really qualify as "aces") he'll be a very strong #2 starter. McDaniel saw Taillon again over the winter at instructs and reported back that he looked basically the same.
The vexing part is that despite having a great fastball and a great curve and a pretty good changeup for a pitcher of his age (he turned 21 in November), his minor league numbers haven't been great. In his minor league debut with West Virginia in 2010, he gave up nearly a hit an inning and allowed nine homers in 92 2/3 innings. Last year with Bradenton, his home runs and hits allowed came down a bit but so did his strikeouts. His K/9 rate in the Florida State League was 7.1/9 innings, which is right around the big league average. That's not quite what you want to see from a pitcher like Taillon at any level in the minors.
The explanation that's mostly been used to explain this is that the Pirates keep their young pitchers on pretty tight leashes in the low minors, limiting how many breaking pitches they throw, stressing fastball command, etc. As a result they can occasionally get hit hard or have lagging strikeout rates, but that those things aren't necessarily reflective of the pitcher's talent so much as the Pirates' method of development. You can see the way that Taillon's being brought along and compare it to, say, Nick Kingham, and understand that he's more talented and that the team is higher on him and that his results are better, even if that's not technically born out in the numbers. Certainly, everyone that watches Taillon throw says that his stuff is still great and that he's still projectible and still on pace to be a good big league starter and all of those things.
All of that being said, questions started cropping up last summer. I distinctly recall Kevin Goldstein, before he left Baseball Prospectus for the Astros, asking when it would be OK to start wondering about Taillon's mediocre results. That it's great that he's talented and it's fine that the Pirates have their own system for developing pitchers, but at what point do mediocre results outstrip immense talent? Taillon quieted some of that with his late promotion to Altoona when he absolutely blew the doors off of the Eastern League to close out the 2012 season. He only made three starts, but in them he struck out 18 and walked one hitter in 17 innings. He gave up 11 hits, no homers, and just three runs. Still, he went from being Baseball America's #15 prospect to #19. At MLB.com he went from #8 to #15. There's nothing wrong with being one of the 15-20 best prospects in the game, but it shouldn't go unnoticed when a prospect's stock drops like that.
I think that the answer to Goldstein's question is that this is the year to really watch Taillon. He's been in the Pirates' system for two years now, he's no longer in the low minors, and he's the same age Gerrit Cole was last year. The leash has to start coming off this year. The first two years in the system, it's understandable that the Pirates wanted to build up stamina and work on command in a high school pitcher. At this point, it's time to transition towards building up an arsenal to pitch in the big leagues. If Taillon's results are still middling with Altoona this year, his prospect stock is going to drop quickly and there will be plenty of reason to worry about his future.
The bigger question, of course, is this: will that happen? I don't really have any more evidence in either direction than what I've already offered. His stuff is still good enough that any scout watching him pitch drools over him, but his results up until now haven't been great. You can read the tea leaves a bit and say that the Pirates letting him pitch for Canada in the WBC is a sign that they're not terribly worried about him and you can put a lot of emphasis on his little run with Altoona at the end of last year, but I'd advise against reading too much into either of those things. I'm going to lean towards breakout, because I find it hard to believe someone with Taillon's talent won't break through and because being negative about Pirate prospects before they've collapsed is the final step towards Total Pirate Apathy and I'm not there yet. My point, though, is that I think that Taillon will start 2014 as either one of the two or three best right-handed pitching prospects in baseball or he'll be out of the Top 50 prospects entirely (or, I suppose, he'll dominate in the minors and get called up early enough to exhaust his prospect status, but that seems unlikely).
From a more zoomed out perspective, what Taillon does in 2013 won't be just about Jameson Taillon. It's also going to be a referendum on the Kyle Stark/Jim Benedict pitcher development program. To this point the Pirates' strategy of taking young pitchers and focusing on fastball control in the low minors has mostly fizzled. There have been a few success storys, but all of the guys that took middling low-minors numbers and translated them into upper-minors success (Rudy Owens, Kyle McPherson, and Jeff Locke come immediately to mind) were all generally relatively low-ceiling guys either drafted by Dave Littlefield or acquired in a trade. It's hard to say whether the system failed guys like Zack Von Rosenberg and Zack Dodson and Quentin Miller, or if the scouting team simply failed to identify high school pitchers that truly had a high ceiling. Taillon, though, has all the talent in the world and even after two years of middling results in the low minors, no real reason to not reach his ceiling. If things don't work out, there are going to be plenty of questions to ask about what went wrong.