The Miami Marlins are lucky to have two of the Top Left-Handed pitching prospects in the minor leagues in their system. Heaney, the 9th pick in the 2012 Draft out of Oklahoma State, made it to Double-A Jacksonville to end his first professional season. Nicolino, a 2nd round pick (80th overall) in 2010 by the Blue Jays, also spent some time in Jacksonville, albeit with less success. Heaney has a legit shot to see an uptick in each category of his report and he already features plus-pitchability. His fastball has been in the 93-94mph range, and his curve already shows flashes of being a 6 and draws a lot of swings and misses. His changeup doesn't get a lot of love in the scouting community, but it has great movement (sink) and could be a great weapon. Nicolino is also very polished for a former high school pitcher, but I'm not sure he has the ability to improve his stuff as much as Heaney does. Nicolino's fastball sits around 90 and his control should stay average. His curveball and changeup both have the ability to become "6" pitches.
I'd give the edge to Andrew Heaney, who could be the top lefty in the minor leagues. He's more polished as a pitcher and he should also have better overall stuff once he finishes developing. His performances have also been better than Nicolino up to this point. Nicolino's got a very solid future ahead of him as well, and the Miami should be able to field a very intimidating rotation in the near future. Both pitchers are probably at least a half-season away from making the Majors, but with the Marlins both could be up quicker.