Miami Marlins' Tyler Kolek makes Baseball America's Top 50

Tyler Kolek could become the next top starting pitcher in the Marlins' rotation. After being drafted out of high school last summer, Kolek was named 46th best prospect in Baseball America's midseason top 50 prospect list. He was the lone Marlin to make the list.

The fastball has backed up a little from the triple digits he showed last year, and he needs refinement.

Kolek, 19, has struggled a bit early in 2015. He has posted a 4.91 ERA and 4.77 FIP through 66.0 innings with Class-A. His velocity, which hit triple digits during his rookie campaign (4.50 ERA, 3.92 FIP), has been down and Kolek has had difficulty throwing strikes consistently at times this season.

Although he has emerged as one of the game's best pitching prospects, the Marlins are not in a position to rush Kolek through their minor league system. Miami has a notable amount of starting pitching depth, and even if Dan Haren, Mat Latos, Brad Hand, or Tom Koehler are dealt, the Marlins would likely receive some form of pitching in return.

Kolek became quickly known when it was clear he possessed a top fastball that occasionally touched 100 mph. However, he is still working on a pitch to get left-handed hitters out, something ESPN's Keith Lawbelieves he needs before taking another major stride.

Kolek doesn't command either of his pitches well, and lacked a real weapon for lefties in high school, trying to backdoor his slider rather than come in with either pitch. His changeup is in its infancy, with the Marlins trying just to emphasize maintaining his arm speed as they work on building consistency in his delivery without making it stiff or slow.

The challenge for Kolek will be learning the finer points of pitching -- command, setting up hitters, mixing pitches -- even though he'll be able to overpower A-ball hitters with pure stuff. I don't think he's a fast mover given how much work there is to do, but there are few prospects anywhere in the minors who look more like a front-line starter than Kolek does.

Kolek has been compared to Josh Beckett and the right-handed starter might not be with the Marlins quickly. But the organization has the depth necessary to enable him to take his time, and despite command troubles, he remains one of baseball's top minor league arms.