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Jordan Zimmermann’s first stint in the American League was a bit of a roller coaster. He started off on fire, with a 5-0 record and a 0.55 ERA in the month of April – the best results in the American League. There were signs of imminent regression, though, with a 2.78 FIP and a 92.3 percent left-on-base (LOB) rate. His strikeout (17.4 percent) and walk rates (5.3 percent) were not up to his usual standards either.
However, his season took a 180-degree turn soon after. Zimmermann posted a 5.74 ERA in the months of May and June before going on the disabled list. He made one start in August, possibly coming back too soon from injury. He once again spent a couple more weeks on the DL immediately afterward before making two more appearances. He finished the year with a 4.87 ERA, 14.7 strikeout rate and a 5.8 walk rate, all low points of his career since becoming a full-time starter in 2011.
Zimmermann primarily throws three different pitches, a four-seam fastball, a slider and curveball. According to Brooks Baseball, since 2011, he has thrown at least 60 percent fastballs, until 2016, when it was down to 52.5 percent. As a result, his slider usage went up from 22 percent in 2015 to 31 percent in 2016. There is a very good reason why his usage was down as his opponents only hit .185 against his slider as opposed to .339 against his fastball.
The batting average against his fastball is alarming and his fastball velocity was down a little in 2016.
| Year | FB velocity |
| 2011 | 93.9 |
| 2012 | 94.6 |
| 2013 | 94.6 |
| 2014 | 94.6 |
| 2015 | 93.4 |
| 2016 | 92.6 |
He consistently hovered around 94 miles per hour before 2015, when he dropped to around 93 mph, and again in 2016 down to 92 mph.
However, Zimmermann does not use his fastball as a strikeout weapon, at least not as often as his breaking pitches. When he really wants a strikeout, he will throw a curveball.
| Year | Fastball K% | Slider K% | Curveball K% |
| 2011 | 18.6% | 22.4% | 22.8% |
| 2012 | 16.1% | 27.8% | 27.0% |
| 2013 | 13.6% | 31.4% | 42.6% |
| 2014 | 20.6% | 33.1% | 32.3% |
| 2015 | 12.6% | 27.6% | 43.2% |
| 2016 | 9.4% | 18.2% | 35.2% |
His strikeout rate on his fastball was down about three percent from a year ago and at the lowest of his career at 9.4 percent. His slider strikeout rate was also at his lowest, 18.2 percent. And even though his curveball strikeout rate was at a high 35.2 percent, it was down eight percentage points from 2015.
Therefore, one would expect his plate discipline numbers to be off a little bit, right? Well according to PitchFX, not really.
| Year | O-Swing% | Z-Swing% | Swing% | O-Contact% | Z-Contact% | Contact% | Zone% |
| 2011 | 29.5% | 63.5% | 48.7% | 66.1% | 90.1% | 83.8% | 56.6% |
| 2012 | 32.1% | 62.5% | 48.7% | 67.2% | 89.7% | 83.0% | 54.7% |
| 2013 | 33.2% | 63.2% | 49.7% | 63.6% | 90.2% | 82.2% | 55.0% |
| 2014 | 36.6% | 64.6% | 51.7% | 67.3% | 86.2% | 80.0% | 53.9% |
| 2015 | 33.5% | 64.3% | 50.0% | 67.9% | 89.8% | 83.0% | 53.7% |
| 2016 | 32.8% | 62.9% | 48.5% | 69.1% | 90.7% | 83.7% | 52.0% |
| Career | 32.5% | 63.2% | 49.3% | 66.9% | 89.3% | 82.6% | 54.7% |
Zimmermann’s swing rate look identical to his career average. Opponents swung at 48.5 percent of his pitches in 2016, compared to 49.3 percent in his career. Those same opponents are swinging at the same percentages of pitches out of the zone (32.8 percent in 2016 compared to 32.5 percent in his career) as well. Their overall contact rate is also very similar.
What is drastically different, though, are his situational stats, particularly with runners in scoring position compare to with nobody on base.
Bases empty
| Year | PA | BAA | K% | BB% |
| 2011 | 411 | .245 | 21.2% | 5.6% |
| 2012 | 461 | 5.288 | 19.3% | 5.2% |
| 2013 | 532 | 5.236 | 20.3% | 5.3% |
| 2014 | 492 | .231 | 24.0% | 3.7% |
| 2015 | 501 | .259 | 21.2% | 4.8% |
| 2016 | 276 | 5.252 | 15.6% | 4.3% |
With nobody on base, Jordan Zimmermann’s batting average against was not too far from the norm at .252. However, his strikeout rate was down once again about five and a half percentage points from 2015.
Now with runners in scoring position, it is a different story altogether.
Runners in scoring position
| Year | PA | BAA | K% | BB% |
| 2011 | 126 | .234 | 14.3% | 5.6% |
| 2012 | 195 | .163 | 20.0% | 6.2% |
| 2013 | 197 | .223 | 16.8% | 5.6% |
| 2014 | 160 | .247 | 22.5% | 4.4% |
| 2015 | 162 | .301 | 17.9% | 6.2% |
| 2016 | 106 | .352 | 12.3% | 10.4% |
Not only is his strikeout down, again about five and half percentage points, but his walk rate went up about four percent as well as a whopping 50 percent on batting average. Opponents absolutely destroyed Zimmermann after they got a few guys on base, a big reason for his inflated ERA.
There are several explanations for why he suddenly struggled with runners on base. It could be moving to a new league. It could be having a different pitching coach with a different philosophy. It could be injury-related, as pitching out of the stretch is different than pitching in the wind up. Luck could even be involved as his 65.7 percent LOB is below the league average of 72.9 percent in 2015.
Regardless of the reason, there is optimism that his numbers could improve given the batted ball data. And given that he now has some experience in the AL under the tutelage of pitching coach Rich Dubee, all he has to do is stay healthy in 2017.