Jordan Zimmermann Has MLB’s Best Fastball


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Of all Major League Baseball starting pitchers, none have a more effective fastball than the one Jordan Zimmermann of the Washington Nationals throws. His four-seam fastball leads all starting pitchers who throw at least 91 MPH in wFB, or runs created by the hitter against a fastball (for more information on this stat, see this article via Fangraphs).

Zimmermann’s fastball is flawlessly controlled, induces a high percentage of outs as well as one of the lowest walk rates in all of baseball–3.2% overall.

With teammate Stephen Strasburg having a rocky start to 2013, Zimmermann has stepped up and become the ace of the Nationals’ staff. And while Strasburg’s fastball is one of the best in the game, Zimmermann’s has been much more potent and has become the best weapon in his pitching arsenal.

Zimmermann relies on his fastball much more than any other pitch in his repertoire, using it 66% of the time on average. The other third is mainly a mix of sliders (thrown much more to lefties) and curves. In terms of velocity, Zimmermann’s fastball is ranked fifth among all starters, averaging 93.4 MPH this season. Despite the above-average velocity, it doesn’t generate a ton of whiffs (just 7%). Throughout his career, Zimmermann has been at or slightly below the league average strikeout rate–currently at 16.4% (19.4% for his career). Batters have taken a cut at the pitch just over 54% of the time and the top five results from contact are groundout (26.7%), strikeout, single, flyout and pop-up. To put its effectiveness into further context, just over one out of every four swings are put in play and 1.2% of swings end in a home run. Pretty impressive for a pitch that generates more home runs than any other.

Zimmermann also ranks 17th in the league in BAA, holding hitters to .204. His fastball has allowed just nine extra base hits–four of which are home runs–resulting in hitters producing a .099 ISO.

The chart below contains pitchers with the most effective fastballs. The data included is a comparison of results on pitches where the (four seam) fastball is utilized:

Pitcher AB 1B 2B 3B HR BABIP K BB Avg ISO
Zimmermann 172 29 4 1 4 .236 24 6 .221 .099
S Miller 157 23 4 2 4 .284 51 13 .210 .115
Harvey 101 19 4 0 3 .348 32 11 .257 .129
Kershaw 189 36 9 1 3 .301 33 14 .259 .101
Bailey 98 17 4 0 1 .309 29 12 .224 .071
Lynn 116 14 6 1 1 .309 47 20 .190 .086
Corbin 70 10 4 1 1 .283 16 5 .229 .114

In relation to the amount of at-bats, Zimmermann’s ratios are as good or better than the other six compared in this chart. Shelby Miller‘s K/BB rate is nearly the same as Zimmermann’s, as well are his hits-allowed type. Though, you  have to take into consideration that Zimmermann has pitched 15 more innings–basically two more starts. Additionally, Zimmermann’s BABIP is by far the lowest, most likely due to the fact that 51% of balls in play end up as grounders.

Zimmermann’s fastball may not blow hitters away, but the way in which he uses it is very effective. While velocity definitely helps, being able to locate–as well as knowing when to throw it–are just as important, and no one exemplifies that better than Zimmermann.