Gregory Polanco was the definition of a pop-up prospect last season. He signed out of the Dominican for a bonus of $175,000 in 2009, and had gone through three professional seasons with a middling performance at best. Through the 2011 season, Polanco had only played three games above the complex level, a short stint at the end of that season in the New York-Penn League. Polanco wasn't expected to be much based on what had happened so far, not being ranked by any of the major publications, including not making the BA Top 30 for the Pirates.
Then the full-season assignment came, and Polanco took off with it. In 116 games at Low-A West Virginia, Polanco hit .325/.388/.522 with 16 home runs, 85 runs batted in, and 40 stolen bases. That performance, coupled with the reports on his defense, vaulted him into the top 100 lists for Baseball America (51), Baseball Prospectus (44), MLB.com (65) and Minor League Ball (50). We ranked Polanco as our #12 fantasy outfield prospect during the offseason, noting the potential for a power/speed combination outfielder.
Polanco missed the final month of the 2012 season due to an ankle injury, and was re-injured after the season as a part of some "quasi-military drills", as reported by Dejan Kovacevic (h/t Bucs Dugout). The ankle injury appears to have healed up just fine so far, as Polanco has hit.307/.370/.486 with six home runs, 27 runs batted in, and 21 stolen bases in 25 attempts at High-A. (This is also occurring in a league which is known for being a pitching-friendly league).
Anticipated Fantasy Value
Polanco's defense has the potential to keep him in center field in the long-term, although he will have value as a prospect even if he does have to move to a corner spot instead. You are looking at a player who is expected to hit for a high average, provide a solid on-base percentage, provide a solid amount of power to go with a high stolen base total. It seems realistic to me that he could have seasons where he hits .290+, 15-20 home runs, with 35+ stolen bases. There have been reports that he could potentially develop even more power, which if that occurred could vault him into the same area as perennial top 15 outfielders.
Long Term Opportunity
Polanco won't turn 22 years old until after this season, and could potentially see AA before the end of the year. Realistically, there is very little reason for the Pirates to rush Polanco to the Majors. You have Andrew McCutchen patrolling center field and under team control through the 2018 season, Starling Marte in left field who won't be eligible for free agency until after the 2018 season as well, and Travis Snider, Garrett Jones, and Jose Tabata around to help hold down the last outfield spot until Polanco is ready. I would expect that we don't see Polanco in the Majors until at least early 2015, with a call up later in that season being a lot more likely.
I'm a believer in Polanco in the long-term, as I love prospects that can show at least solid production in three categories. Add in that he's been doing this in a pitchers' league, and I think he could actually move even further up top 100 lists this offseason. He is likely to be owned in most leagues with some form of a minor league draft, but there may still be the opportunity to get in before his value skyrockets even further.