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Back in November of 2015, Jordan Zimmermann was one of the top arms on the free agent market. When the Tigers offered him a $110 million deal, it was hard to bellyache as that’s what many thought he would get on the open market. Now, well past a year since the deal was signed, it’s looking very clear that the deal was a mistake for the Tigers.
Prior to his time in Detroit, Zimmermann cemented himself as a top-of-the-rotation arm. From 2011 through 2015, he led the Nationals rotation along with Stephen Strasburg. He consistently posted around 200 innings a year and was a 3.6 pWARP/200 pitcher over that time span.
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Despite that, he carried concern over his injury history, usage, and general career trajectory. Zimmermann underwent Tommy John surgery in 2009. The injury reared its ugly head as he went into free agency. As he experienced a fairly off year in 2015, the question of whether he would go under the knife again legitimized itself. Even without that, Zimmermann was entering his age-30 season. Presumably, his decline would begin well within his next contract.
Now, it’s clear that a cliff was there and he took a step off it. Last season, his 5.14 DRA and 14.7 percent strikeout rates were both significant worsts for his career. This year, things have generally gotten worse, with his HR/FB and DRA both ballooning. On top of that, he’s on pace for a career worst walk rate, and only a 1.3-percentage point rebound in strikeout rate.
When you take things at a more granular level, it’s easy to see where the siphon is coming from — his fastball and changeup. Zimmermann is essentially throwing less strikes while also not getting enough whiffs to make up for it.
Jordan Zimmermann - Strikes and Whiffs by Pitch Type
| Timespan | Fourseam - Whiffs | Fourseam - Strikes | Change - Whiffs | Change - Strikes | Slider - Whiffs | Slider - Strikes | Curve - Whiffs | Curve - Strikes |
|---|---|---|---|---|---|---|---|---|
| Timespan | Fourseam - Whiffs | Fourseam - Strikes | Change - Whiffs | Change - Strikes | Slider - Whiffs | Slider - Strikes | Curve - Whiffs | Curve - Strikes |
| Pre-Contract | 7.66% | 68.70% | 7.19% | 64.87% | 15.82% | 71.60% | 10.55% | 61.30% |
| Post-Contract | 6.05% | 64.82% | 9.24% | 57.82% | 14.66% | 71.87% | 8.60% | 61.08% |
Moreover, his overarching issue is partially driven by his fastball becoming less effective.
Zimmermann Fastball
| Timespan | Usage | GB% | FB% | HR% |
|---|---|---|---|---|
| Timespan | Usage | GB% | FB% | HR% |
| Pre-Contract | 64.52% | 7.83% | 4.49% | 0.65% |
| Post-Contract | 49.94% | 5.46% | 6.57% | 1.50% |
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With a dip in velocity over a mile per hour on average that started in 2015, his fastball hasn’t been the weapon it once was. From his zone profiles, it’s clear his tendencies haven’t really changed much at all with fastballs outside of usage. However, the tables above show that the effectiveness of the pitch has been absolutely hammered since coming to Detroit, with much less desirable contact spiking since his arrival.
Since his fastball velocity is down, Zimmermann has tried to shift his usage elsewhere. He’s thrown much more breaking pitches and has even introduced a sinker, but those pitches haven’t been as effective. His ability to pitch off his fastball in the past was what seemingly brought him to the limelight. Without the effective heater, he hasn’t been able to adjust his repertoire to fool hitters.
Zimmermann’s velocity dipped, which is a common ailment for aging pitchers. His issue was that he couldn’t adapt to it. That’s entirely reasonable. It’s hard to make up for a full tick or more on your fastball without losing a bit of luster. But, Zimmermann has taken such a tumble that he might not even be around to see another contract. While the Dan Harens of the world adjusted to become at least serviceable back-end arms, Zimmermann is struggling to even become a replacement level pitcher.
Anthony Rescan is a Featured Writer at Beyond the Box Score and is a Stats Intern at Baseball Prospectus. You can follow him on Twitter at @AnthonyRescan.