I'm not sure any Cub of the past 10 years is more enigmatic than Juan Carlos Paniagua (JCP for short). He's been "signed" 3 times, and the first 2, questions about his age (questions being used rather euphemistically) resulted in suspensions and deals being rescinded. He was signed the first time by the Dbacks in May 2009 (as Juan Carlos Collado) for $17,000, then after a year suspension signed for $1.1 million with the Yankees, was suspended another year for falsifying paperwork again, and then signed for good on July 19, 2012.
As you could imagine, the MLB took it's sweet, sweet time in doing his paperwork for the third time. It also took forever for his visa to clear, so while he was expected to debut at the beginning of the year, he didn't get stateside until July 8, 2013.
As a 23-year old, you'd expect JCP to dominate basically anywhere he went short of AA on up. That isn't what happened. He played a lot in the DSL (and he was excellent there in 12.1 innings), but he only pitched 21.2 innings above rookie ball and was quite underwhelming in all of them. He allowed 25 runs in those 21.2 frames, walking 24 and striking out 24 as well. Those are gross numbers, and it's best to just imagine he didn't pitch at all (and considering his 4 stops, his visa, and everything, he basically didn't).
Luckily, there's some solid scouting on Paniagua (seeing as he signed essentially 2 major contracts). I'll concede to the inimitable Ben Badler, who is the preeminent source on international prospects:
Paniagua hasn't shown the same velocity he had when he signed with the Yankees—he sat at 93-95 mph at a May workout in Puerto Rico—but his 81-84 mph slider has improved after some scouts last year thought it was a slurvy pitch that graded out behind his changeup. He also throws an occasional curveball, and while he was around the plate in Puerto Rico, his command and pitchability have been issues in the past.
Comically, Baseball Prospectus still has him as Juan Collado in their system. They've never once mentioned him, which seems incredible considering he's not an NP. Baseball America also had little to say, and what little they said about him this year was quite negative.
All of that being said, I don't really care. He's 6'1", 175, so his 93-95 heater (which was up to 98 at the time of the Yankees signing) could even gain a mile or two as he fills out (and accounts are that he is getting bigger). He has 4 pitches so he's a threat to start, but as a 23-year old, it's probably time to seriously consider a permanent move to the bullpen, where he could likely return to 98 mile cheese and a hard slider. That generally is the arsenal of a closer.
JCP has, frankly, been very disappointing since he signed the contract. Some of that is his fault and some of it isn't. In any case, he's a 24-year old who hasn't shown he can handle even A ball, so he just isn't much of a prospect at this point. He'll likely start the year as a reliever in Kane County, and if he dominates, he'll be promoted extremely aggressively. If he doesn't, at least he cost 5.5 million less than Gerardo Concepcion!