Don’t worry too much about Lance Lynn’s return from Tommy John Surgery

It’s been a while since we’ve had the pleasure of watching Lance Lynn pitch. For a while he was looking like one of the most under-rated pitcher in baseball, accumulating nearly 13 fWAR from 2012 to 2015, 20th among pitchers in that time frame. 2015 was Lance’s most fastball-happy season yet (82%), and his mastery of the pitch earned him national recognition.

That’s when news broke that took the wind out of the sails of many a Cardinals fan: Lance Lynn needed and received Tommy John Surgery following the 2015 season. Not only that, Lynn had pitched with a bad forearm since June. It went a long way towards explaining why Lynn pitched to a worse than average 4.33 FIP in the second half, much worse than usual for the consistent performer.

Lynn explained that it was worth it to pitch the rest of the year with an injury, because either way he was going to miss all of 2016. And that he did, though he did manage a rehab assignment late in the year. That hopefully allowed him to have a normal off-season and the expectation that he would be back at 100% come April 2017.

Will he though? Throughout baseball, there is an expectation that pitchers aren’t quite themselves in their first year back from Tommy John. Loss of feel, stuff, and command are all commonly cited problems. Cardinals fans can look back at 2012 Adam Wainwright and 2014 Jason Motte as examples of pitchers who just weren’t who they used to be.

I’m a numbers guy, so naturally I wanted to quantify something. Luckily, Jon Roegele of MLB Player Analys had my back with a spreadsheet containing a large list of those who had had baseball’s most popular surgery. My plan was to use this list, along with Fangraphs leaderboards, to see what I could find about how Tommy John Surgery affected pitchers after returning.

My analysis here isn’t perfect. Ideally, I’d be able to track something like the last 100 innings before Tommy John Surgery to the first 100 innings coming back. I don’t have a systematic way to gain all that game log data, so I had to approach it on a seasonal basis. What I did was this: First, I had to determine a “Lost Year” from each Tommy John Surgery recipient, based on when he had the surgery. If he had the surgery in-between seasons, his lost year would be the season he was just about to pitch in. April or June would mean his lost year was the one he had just started. July through the rest of the season would mean the following year was lost (even though there’s a chance he could pitch some at the end of it). I did this for all seasons from 2004 to present.

With a loss year set for each pitcher, I then culled the list provided down to those that had thrown 20 MLB innings the year before the lost year, as well as after. Now, I plan to do a few things with this data, but today we just had one question to ask: On average, how did Tommy John recipients do upon return to the majors, relative to their past production? Turns out, not near as much as what is commonly assumed. Of a group of 73 players, the average gain in FIP was just 13 points. Over a 200 inning sample, that’s 3 ¹⁄₂ to 4 runs.

It’s not that simple though. When players enter the league, they’re already in decline, on average at least. Just taking a simple average, the average decline from 22 to 38 for pitchers is about 3 runs per 200 innings. So when considering this is comparing data two years of aging apart, those returning from Tommy John Surgery actually age less than expected! It’s still not actually that simple, as the run scoring environment shrank during most of the time period we’ve look at, but it at least shows that Tommy John doesn’t come with a strong chance of posting weak numbers in a pitcher’s return year.

It gets even weirder when looking at just starters. I looked at those that threw 50 innings as a starter in the years before and after their lost year. It yielded a sample size of just 21 pitchers, but those 21 on average lost 13 points of FIP. We shouldn’t take that result all that seriously with such a small number, but its interesting nonetheless.

The first run included 73 pitchers. That was culled down from an original list of 216 from the source data linked above. Some pitchers had just come up from the minors, and thus hadn’t pitched the required 20 innings the year before. Some were fringe talents that had to wait an extended time period for their next chance at an MLB role. Some had injuries the year before or after. Some waited to have the surgery, hoping rehab would be enough, leading to less innings the year before. Some probably just were missed by my programming code just from having slightly different names in the data. The use of Jr. or not can really affect this sort of thing, and is something I’ll have to manually fix when I have more time.

You might assume some were left off because they had to get another Tommy John Surgery after the first. While that’s true, it wasn’t all that likely. Of the 216 different MLB pitchers to have a Tommy John Surgery in the majors, only 16 have had a second while in the majors. Of those 16, only 9 had two less than two years apart. Of course, many more have had more than one Tommy John Surgery when including their time in the minors, college, and high school. The point, is, needing one right after coming back is pretty rare (under 5%).

Charts with The 73 and 21 players on it don’t really make sense to paste into the article here, so here’s a link to a spreadsheet with the results. There’s certainly more ways we can look at this data to get a better understanding of how Tommy John Surgery recipients change. This analysis at least shows that we don’t have to fear that Tommy John Surgery significantly worsens a pitcher’s performance. Lance Lynn will be a year and a half older than the last time we saw him take a mound, and we should probably downgrade our expectations a little bit because of that. However, don’t mentally downgrade him because he’s coming back from Tommy John Surgery, because it doesn’t seem necessary.