If there is one thing that has been guaranteed with Kelvin Herrera, it is his electric fastball. That fastball averaged 98.13 MPH last season, and was better as the season wore on. By the time that September rolled around, Herrera was averaging 99.31 MPH with the heater. Add in a change that typically came in approximately 12 MPH slower, and it is easy to see why Herrera shows signs of being a dominant force in the back end of the bullpen.
Although Herrera is typically a fastball/changeup pitcher, throwing those two pitches around 70 to 80% of the time, he has mixed in a sinker as well. Yet, it appears that Herrera is not satisfied with that repertoire. This offseason, as he spent time in the Dominican Winter League, Herrera spent his time working on sharpening his curveball. In his time pitching for Escogido, he appeared in five games with three starts, putting together a 1.93 ERA with 12 strikeouts in 9.1 innings of work.
While it is certainly great that Kelvin Herrera is looking to improve, and to find other ways to get the opposition out, is working on the curve the best way to go? Herrera used that pitch under 8% of the time last season. When he did utilize the curve, it was effective, as the opposition only produced a .188 batting average against the curve. Meanwhile, Herrera used his sinker 15.18% of the time last year, yet opponents produced a .294 batting average against that pitch.
Perhaps Herrera is looking to scrap the sinker. Despite his excellent 2012 campaign, he did not have a lot of success with the sinker that year either, as opponents had a .317 batting average against that pitch. Yet, although Herrera did not use the curve nearly as much, his success improved, as the batting average against the curve dropped 112 points.
It may be that, instead of looking to add a fourth pitch to his arsenal, Kelvin Herrera is looking to upgrade what he has. Should his curveball be that much improved over last season, when he got far better results than he had the year before, Herrera may have a three plus pitches to choose from, making him an even more lethal weapon in the eighth inning. After the inconsistent year he had in 2013, changing to the curve may help Herrera perform better in 2014.
With the questions surrounding the back of the Royals rotation to start the season, the bullpen may be a major factor in determining their success this season. Having a more consistent Kelvin Herrera can only strengthen what was already an excellent group last season. Perhaps sharpening his curveball is what it will take to get him there.