Playing Through an Injury Hurts Future Performance

I was wrong. About seven years ago, I wrote on how hitters may overperform their projections since they played through an injury. The injury hampered their production in the season in question, lowered the future projection, and created a buying opportunity. For years, I believed this steadily until last season when I re-ran the numbers and found “jack squat”.

Earlier this week, I examined some of this past season’s hitters who fought through the pain and felt a deeper analysis was needed. I dove in and the results were backwards. I found no bounceback should be expected from hitters who played through injuries, but there is more. For those hitters who play through the discomfort, their future production will take a major hit.

The key to uncovering the following results was getting a usable dataset which is easier said than done. Many of the injuries I’m using for the analysis aren’t well documented, if at all. Real men play baseball and they play hurt because that is what real men do and most importantly, they don’t complain about. Besides the machismo, a player has every right to keep his medical data to himself so vagueness thrives. Simply, there is no good available data. Even with the hurdles, I dug into each of the hitters who were reported to have played through an injury the past three seasons (2017, 2018, 2019).

For all three seasons, I went back and read through the linked article for the date and details of the injury. In many instances, I had to go to RotoWire and comb through the old news and I can’t thank them enough for providing this resource. For each player, I tried to find the exact date of the injury along with the following OPS values (*):

• Steamer Projection for the season the injury occurred
• Before the injury
• After the injury
• Steamer Projection for the season after the injury
• Results for the season after the injury

The in-season analysis utilized all three years of data and the next year’s analysis excludes the 2019 data. In some instances, the injury happened in Spring Training or immediately into the regular season and no before-and-after data exist. That’s enough background, it’s time to dive in.

The first comparison is how the hitters performed before-and-after the injury during the season of the injury.

The performance drop is noticeable and consistent across the three seasons. For fantasy owners, they need to be wary if they hear a hitter is banged up and should expect a noticeable performance decline.

Next up is how these hitters performed compared to their preseason Steamer projections. Besides the overall numbers, I divided up the players into those who were hurt the entire season and those for just a fraction of it.

No surprises appear in the above data since those hitters who had the injury longer saw more of a decline.

And now for the money table. Here is how the hitters hit in the season after the injury. While I did split the data up some, I feel the sample is too small to split a split. Maybe in the future more can be done. Additionally, I created a metric out of thin air to help determine how much the injury may have hampered the player. In the end, I decided on:

Injury Effect = (Days from Injury to End of Season)/183 x Change in OPS * 1000

I used -40 as the dividing point between “Short & Little Effect” and “Long & Large Effect”. I know it’s not close to perfect but it at least gave me a way to divide up the players.

So the results are completely opposite to what I thought for years, playing through an injury doesn’t mean a rebound is coming the next season. Additionally, the players who played through a more severe (measured in OPS decline) injury longer, experienced even more of a decline than those who had a small injury for a short time.

Unsurprisingly, the hitter’s age matters. The younger players are able to main the projected stats. The projection already has an average aging factor incorporated into it, so the players over 30 will see a major decline. These findings follow some of my previous works where I found players who didn’t go on the DL/IL didn’t age as fast.

While I try to incorporate injury information into my analysis, I have zero medical training so I decided to elicit some expert help on the subject to see how my ideas held up. Dr. Mike Sonne (@DrMikeSonne on Twitter) believes there are two factors working against people who play through injuries. The first is that mild to moderate injuries can escalate into severe or chronic ones. Patients who put off needed rest or surgery can make the problem significantly worse.

The second factor is that the players develop alternative body movements to deal with the discomfort. The altered movements aren’t as effective and efficient as the original ones that got the hitter to the majors. When the player can finally rest and recover during the offseason, the new inefficient movements have taken hold and therefore degrade the player’s future production.

Additionally, Dr. Jesse Morse (@DrJesseMorse on Twitter) shed some insight on what any “mature” person already knows, the body takes longer to heal the older it gets. The average person heals slower starting in their early-30’s and the drop is really steep once a person reaches their mid-30’s. He emphasized several times that most baseball players are the exception to many physical rules and will exceed many norms well into their late 30’s (e.g. Nelson Cruz).

While the overall trends can be verified, Dr. Morse emphasized how each player eventually performs will be determined by the exact nature of the injury. Several times I read that a player is “dealing with a sore knee”. The soreness can be from a ligament, muscle, bone, meniscus, or some combination of each.

Going into next season, the players to worry about are listed in the table at the end of the article which includes several top picks like Trea Turner, Cody Bellinger, and Javier Báez. While the three are young, they did deal with the injury for almost the whole season. The only way to see how each player responds is to play out the season, but owners should know the downside with each.

Gutting through an injury can make an it worse and accelerate the aging process. As fantasy owners, it’s not our call to decide if the player is right or wrong for playing through the injury. We just need to know to expect less from them in the future. No rebound should be expected.

(*)

* Found out about injury after the article
Maikel Franco (link)

Brandon Nimmo, neck (link)