Who is the Real Marcus Semien?

Is he for real or a sell-high candidate?

Marcus Semien picked the wrong time to become a free agent. Well, he obviously had no control of the situation. But, he had to settle for a one-year deal this offseason with Toronto despite hoping for a long-term deal. Naturally, MLB’s billionaire owners used a shortened COVID season as an excuse not to spend as much money on last winter’s free agents, which led to many other players having to settle for underwhelming contracts, like Semien.

Unfortunately, Semien will now enter a new free agency class that may play out even worse for him, through no fault of his own. While he is in the hunt for, and probably deserves, a big payday, this class is loaded with middle infielders. It will be difficult to compete with Corey Seager, Trevor Storyand Carlos CorreaWe know only a handful of owners are truly willing to open their wallets to give their team a better chance to compete for a championship, so it’s hard to predict what Semien’s market will be.

To call Semien’s career thus far a roller coaster ride may be an understatement:

Marcus Semien wRC+ by Year

Believe it or not, this is just Semien’s second season with above-average offensive production. He is certainly a different player than he was in 2018, and 2020 was over a small sample, but we can’t completely ignore those seasons. It’s not like he has a long track record of success as a major league hitter for us to fall back on. Semien is definitely somewhere in between slightly below average and great as a hitter. That’s a large range. But, where does he fall within it?


Some Things Never Change


Shockingly, through good times and bad, Semien’s plate discipline profile has essentially stayed the same his entire career.

This is about as consistent as you can get in a nine-year career. You can say virtually the same about his zone contact rate, which has remained around 82%. His walk and strikeout rates have been a bit more varied, but these metrics are naturally noisier. Walks and strikeouts take more factors into effect than a chase or a whiff, which describes what happens on one individual pitch. Both of these figures are below average for Semien, so he has relied on his quality of contact for success at the plate.




If you play fantasy baseball, I’d argue there’s not a single concept you need at least some sort of grasp on more than regression. By now, we all know that a player’s production, especially over a small sample, is not necessarily indicative of their talent. Semien is a very odd profile to study. Is this season’s explosion an example of positive regression from last season, or is he performing above his talent level and negative regression is on its way? It’s probably a little of both. Let’s take a look at how Semien looks on the metrics I use as regression indicators:

Marcus Regression Indicators


He has overperformed his xwOBA every year, which is usually seen as a bad sign, but xwOBA isn’t really a predictive stat. So there’s much more to evaluate. Line drive rate is usually an indication of how relevant a player’s xwOBA is from a predictive standpoint. When a player’s line drive rate is very far off from the league average, in one direction or the other, it may drag their xwOBA and signify regression. Semien’s LD% has been close to average each of the last four years, which makes the difference between his wOBA and xwOBA important. You can read about sd(LA), or “launch angle tightness”, here.  Essentially, players whose launch angle distribution are tighter (have a lower standard deviation), are more likely to see sustained success in the future. Semien’s numbers are once again pretty average in this statistic. All of these metrics point to Semien being closer to an average hitter than he is performing this season.

Marcus Semien Batted Ball Distribution

Semien’s pull% has gone up significantly this year. This is massive, specifically for a player like Semien, who hasn’t hit the ball very hard over the course of his career. Pulling the ball can help turn some of those softly-hit balls that were previously outs in the opposite field into harder-hit balls on the pull side. However, pull rate is even noisier than line drive rate, which adds even more fuel to the argument that he is currently overperforming. Recently, Alex Chamberlain looked into using spray angle to create a dynamic hard-hit rate, rather than the static 95 MPH that is currently used (an extension of Connor Kurcon’s work). Spray DHH%, the name of the stat coined by Alex, is slightly better at predicting future success than traditional HH% and is additionally more sticky year-over-year. Here is what Semien’s Spray DHH% looks like in his recent years, as well as the percentile among the rest of the league for perspective:

Spray DHH% By Season

Final Thoughts


I think we can all agree Semien’s true talent level lies somewhere between his production last season and this season. However, it seems as if he is closer to an average hitter than this year may indicate. Now, that’s not to diminish his market value as he hits free agency for the second consecutive offseason. He’s been one of the best defensive second basemen in baseball this year, and his positional value as a middle infielder helps boost his offensive status. However, from a fantasy standpoint, I think I’d sell high on Semien if you can. 

Photo by Joe Robbins/Icon Sportswire | Adapted by Aaron Polcare

Jeremy Siegel

Jeremy is currently a senior studying Computer Science and Statistics at the University of Pittsburgh. He is a writer and data science staffer here at Pitcher List. His goal is to one day work in the analytics department of the front office of an MLB team

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