Cesar Puello makes his mark at number four on our list. Puello is widely considered to be the best outfield prospect in the organization after three years in the minor league system, and he is the highest ranked outfielder on our list. He played 109 games for Savannah last year at the age of 19, playing exclusively in right field. He struggled throughout most of the first half hitting just .249 as Savannah, hitting mostly in the bottom half of the lineup for a Sand Gnats team that won its division in the first half of the season. Part of the reason for his struggles is that he spent time re-working his swing, which caused him to have a pitiful May hitting .192, but then paid big dividends for him in the second half. With Savannah’s better hitters getting promoted mid-season, Puello was thrust into the heart of the batting order and started tearing it up, hitting .303 in June, .356 in July, and .347 in August, while having a multitude of multi-hit games. Puello also has great tools beyond his bat. He has great speed that gives him range in the outfield that goes nicely with his strong arm, making him an asset defensively. His speed also allowed him to steal 45 bases last year.Puello will be just 20 years old on opening day, but judging from his second half in Savannah last year, he should get the promotion to high-A St. Lucie, where he should expect to spend the whole season. At his age, there’s no reason to rush Puello, so he should get at least two more full years in the minors before there’s any thought of him seeing Citi Field. In the meantime, there are a couple things to keep an eye on as he develops. One is his defensive position. There are some who believe that Puello has a chance to be a centerfielder, which would increase his value. Whether or not the Mets play him in centerfield at some point is still yet to be seen. The other part of his game to watch is his power. Puello hit just one homerun last year, and has seven in his three-year career. If his power does not come along then a move to centerfield would be more likely, and allow him to retain his high value; however, if Puello does develop a lot of power, he could enter the big leagues down the line as the classic 5-tool player who would fit in anywhere in the outfield.