Keep in mind that this is not a traditional top prospect list because it focuses entirely on 2013 contributions. I rank guys according to advanced metrics which, for position players, include batting runs above average, positional adjustment, defense, and a replacement level calculation that scales the total to "Wins Above Replacement" (though the concept of replacement level doesn't really apply to minor leaguers). I use a standard "runs allowed based" WAR formula for pitchers.
(2) Mark Sappington, 22, rhsp. A+/AA. 4.6 WAR, 25 runs saved. 156.1 IP, 3.45 ERA, 136 K/82 BB
Man, do things change. Sappington's a good prospect: he's advanced as quickly as you could expect a 2012 fifth rounder to move, and has already held his own in the upper minors. He throws mid 90's gas and shows flashes of a good slider and change-up, giving him number three starter upside. Definitely a good guy to have in the system.
But man; this is it. Sappington may look like our best hope for a cheap, home-grown rotation arm north of rookie ball, but he's a long way from a sure thing. His 2013 campaign echoed a trend that goes back to Nick Maronde, Tyler Chatwood, and Trevor Reckling, where a guy breezes through High A and appears to ‘pass' the AA test with a sparkling ERA but lagging peripherals. The common theme here is that those pitchers were nowhere near as good (yet!) as their Texas League ERA suggested. Chatwood required another two and a half seasons of incubation before succeeding with the Rockies, Reckling regressed significantly after his 2011 Texas League ‘breakout,' and Maronde still hasn't figured out how to miss right-handed bats despite ‘succeeding' in the Travs' Dickey Steven's Park. In each of those cases, and many more besides, the peripherals have been a much better indicator of present skill, while ERA or RA-9 measures have been worse than useless. With that in mind, we're left to judge Sappington's merits on the peripherals and the scouting reports, and those data points depict a guy who's more lottery ticket than blue-chipper. Moreover, he's the only lottery ticket remaining in the system who's sniffed success in full season ball and isn't spending 2014 recovering from surgery.
(knocks wood frantically).
Sappington has a rigid, high-effort delivery, which makes for the difficult command profile that loomed behind what was an otherwise promising 2013 campaign. His California League assignment was an aggressive move on the Halos' part, but he thrived through April, fanning nearly a quarter of the guys he faced, posting a 50%+ groundball rate, and walking fewer than 10% of hitters. That was by far his best month of the year, and he accrued almost half of his overall value in that time. His control slipped significantly in May and June, when the walks ticked up, his k-rate plummeted almost 50%, and his groundball rate dropped by a third. He appeared to right the ship in July, but even then, the free passes continued to mount. His walk rate climbed to almost 17% in August, after he received a promotion to help with the Arkansas playoff push. For reference, no major league starter walked more than 13% of opposing hitters in 2013. Yet, despite the walks, he muddled through with a 3.86 ERA. How sweet it is to be a pitcher in the Texas League.
Mechanics and command aren't the only reasons for why folks have been quick to throw the "future reliever" tag at Sappington. His secondary pitches are inconsistent, eliciting vastly different reactions from evaluators depending on who sees him when. Everyone likes the fastball, but the breaking stuff received some tepid reviews (here and here) amidst some decent ones. Opinions really vary around the quality of his change-up: no doubt it improved over the course of the season, and Baseball America now calls it his second best pitch, but its late development and inconsistency still have folks questioning whether or not Sappington can put together a consistent three-pitch mix.
Sappington's fastball and rapid development provide some hope that he's ready to join the Halos' rotation by mid 2015, and it wouldn't surprise me at all to see him get a spot start or two before then. However, he's by no means a lock, and odds are against him putting it all together sufficiently to stick in the rotation. History just has not been kind to starters with his walk rate. That said, the good fastball makes him an attractive bullpen piece, perhaps starting as soon as mid 2014.