As part of the new era of pitching, baseball has ushered in a wave of young fireballers who dominate through velocity. Aroldis Chapman, Stephen Strasburg and even unheralded arms like Kansas City's Kelvin Herrera routinely hit 100 mph with their fastballs, and baseball has never been so populated with as many hard throwers as there are today.
However, on the other end of the spectrum, there is a group of pitchers making a splash in the big leagues with stuff that would fit in better at your local high school. Tommy Milone (Oakland), Mike Fiers (Milwaukee), Carlos Villanueva (Toronto) and Scott Diamond (Minnesota) are all establishing themselves as big-league starters and rewarding their organizations for taking a shot on a guy without a big fastball. Milone's success after being just the extra guy added into the Gio Gonzalez trade is one of the main reasons why the A's are surprise contenders, while Diamond, Fiers and Villanueva have all been pleasant surprises on pitching staffs that found themselves desperate for reliable midseason pitching.
As a group, their fastballs have averaged just 88.5 mph this year, with Diamond being the hardest thrower with an average velocity of 89.5 mph on his fastball. However, they are all very different pitchers and succeeding in very different ways. Diamond is a sinkerball specialist who generates a ton of ground balls, while Fiers is one of the most extreme fly ball pitchers in baseball. Milone is a control specialist who never walks anyone, while Villanueva has the 11th-highest walk rate of any pitcher in baseball with at least 60 innings pitched this year. Despite the stereotype of every low velocity starter being cut from the same mold, these four are all pretty different.
Of these four low velocity hurlers, is there one whose skill set portends success more than the others? Let's take a look at some historical comparisons for both. (For our purposes here, BB%=walk rate, K%=strikeout rate and GB%=ground ball rate.)