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A tale of two Miguel Gonzalezes in 2015: before and after his injury

Miguel Gonzalez struggled in 2015 posting his worst career numbers. He went down in early June with a groin injury that may have affected his performance throughout the rest of 2015. Below is a lot of numbers and charts attempting to find out if that happened.

Tommy Gilligan-USA TODAY Sports

I have written many a word on Miguel Gonzalez before. He has been one of the more enigmatic pitchers in baseball over the last four years. Posting great results (shiny ERA numbers), but mediocre peripherals (poor Fielding Independent Pitching numbers, (FIP)). In 2015, the results finally matched the peripherals. Plain and simple, he stunk, posting a 4.91 ERA for the Orioles in 26 starts. If the Orioles hope to get back to the playoffs in 2016, a pre-2015 Gonzalez will be of the utmost importance.

So I did some research to figure out what happened in 2015 and I noticed that he posted a 3.33 ERA before June 9th of 2015, the date he strained his right groin and pitched to a 6.53 ERA after coming back from the disabled list on June 25th. So the basic results paint a picture of a player who either struggled to get back to 100 percent healthy or a pitcher who could never regain his rhythm after some time off from injury. I wanted to dig a little deeper.

First, below is a table of some basic numbers to see if anything stands out from before and after his groin strain. The Before DL numbers are collected from his 12 starts on and before June 9th. The After DL numbers are collected from his 14 starts on and after June 25th. His career numbers are also listed for some context.

Before DL 3.33 4.63 19.8% 8.1% 82.2% .235 14.7%
After DL 6.53 5.39 15.4% 8.3% 67.1% .348 15.3%
Career 3.82 4.70 17.1% 7.8% 78.3% .272 12.1%

As one can see, his ERA jumps over three runs in his 14 starts after his time on the disabled list. Also, his FIP jumps as well, but only by about 0.8 runs. Much internet ink has been spilled over whether or not Gonzalez is the pitcher his ERA says or the pitcher his FIP says. Again, I myself have written about the topic on these very pages. Personally, I am of the belief that FIP cannot tell the whole story with Miguel Gonzalez.

You will also notice that his strike out rate drops precipitously and his walk rate crept up a tiny amount after the groin injury. Meanwhile, his LOB% falls fifteen percentage points after his time on the DL and was below his career rate by eleven percentage points. Although, Gonzalez's LOB% has also long been given as a reason for his good results. His carer number is very high high as league average floats somewhere between 70-75%. So he may have simply been lucky to strand the runners he has in his career, rather than accomplishing it through actual skill. Again, I do not think that gives a complete picture of Gonzalez, but it is something to consider.

Also, his BABIP was at a very low .235 before the DL and skyrocketed to a .348 post DL.  Both of those numbers are pretty extreme, but that may indicate some some bad luck or hard contact after the his time off from injury. His BABIP on the season ended up at .295, way above his career number of .272. Which again, it is possible his career number is low due to good fortune.

So, those numbers tell some of the story, but not all of the story of Gonzalez's 2015 season. Below are his batted ball numbers divided up into the same three categories.

LD% GB% FB% IFFB% HR/FB Soft% Med% Hard%
Before DL 23.9% 40.2% 35.9% 9.3% 14.7% 18.5% 53.6% 28.0%
After DL 23.9% 40.3% 35.7% 9.4% 15.3% 15.2% 55.1% 29.6%
Career 22.0% 38.1% 39.9% 11.5% 12.1% 17.8% 53% 29.2%

As one can see, his batted ball types (line drive, ground ball, fly ball,and infield fly ball) all remain relatively the same from before and after the injury. However, his soft contact rate falls around three percentage points which is redistributed to both medium and hard contact. So, he was surrendering harder contact after his groin injury. Furthermore, his before the injury numbers line up better with his career numbers. While the numbers are not staggering, there would certainly be a negative effect for a fly ball heavy pitcher such as Gonzalez to start giving up harder and harder contact.

After looking at all of those numbers I thought that maybe his command had struggled. His strike out rate dipped after the injury, but the walk rate stayed basically the same. Yet, command is trickier to measure than simple balls and strikes. Below is a chart of Gonzalez's 2015 plate discipline numbers. Again, the three time periods are the same. If you have any questions about what each column means, please consort the Fangraphs Glossary, which is a fantastic guide to sabermetric statistics and concepts.

O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% Zone% F-Strike% SwStr%
Before DL 34.0% 70.7% 50.0% 68.5% 86.9% 79.8% 43.5% 61.4% 10.0%
After DL 34.5% 68.7% 48.6% 74.9% 89.9% 83.7% 41.3% 62.7% 7.9%
Career 33.1% 68.6% 48.5% 72.9% 88.6% 82.5% 43.3% 61.6% 8.4%

His contact numbers clearly get a little worse across the board in the second half of his season, but they line up more with his career rates. The only ones that differ in any meaningful way are his rate of pitches in the strike zone and his contact rates especially the contact rate on pitches in the strike zone (Z-Contact%). His zone rate is lower than his career average and his Z-Contact% is higher. That could indicate some poorer command throwing more pitches not in the strike zone and the pitches that do make it to the strike zone getting hit more often.


It is all about as clear as mud. Some numbers point to the injury being a point in Gonzalez's season where things went awry. Some point to it not being all that important at all. I dove deep into some Pitchf/x data attempting to find some change in his delivery or stuff, but after blood started pouring out of my nose and ears I could not find anything truly meaningful. Some spikes hear and there, but nothing consistent and nothing that made a lot of sense, so I spared you all some superfluous charts. If you want to take a crack at it, go over to Brooks Baseball and click away.

If had to come up with a conclusion, which is why they pay me the invisible big bucks, I would argue that the injury did affect Gonzalez and hurt his overall performance in 2015. He came back relatively quickly from an injury that can hamper a pitcher for a long time. If he was not 100 percent when he came back, he could have altered his delivery in the slightest which would throw off his command and allow harder contact. Furthermore, the repetitive nature of pitching is such that even a change made when not 100 percent, could linger long past the actual injury. I think the numbers above play out that narrative, not perfectly, but I'll fit the squarish peg into the roundish hole.

Miguel Gonzalez is a pitcher that thrives off an ability to generate weak contact, especially weak fly balls. His career high BABIP, high contact rate, low zone rate, and low soft contact rate all indicate to me that something happened to him after his groin injury and time on the disabled list that somehow negatively affected his performance on the field. Now I just have to figure out what.