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February 25, 2021
In the long arc of baseball history, there is no precedent for Marcus Semien. Spend a day checking the statistical record: you won’t find anyone like him.
From 2013 to 2018, Semien produced a triple-slash batting line of .249/.310/.403. Adjusted for league and park effects, that tallies to an Adjusted OPS (OPS+) of 96. Semien’s Weighted Runs Created Plus (wRC+) was identical: 96.
That 96 is a percentage, of course: it measures his offensive production against the league average. Marcus Semien’s skills as a hitter, adjusting for park effects and league contexts, were a few ticks below the major league average.
His OPS+ and wRC+ were again identical last season: 91 and 91. During the weird 2020 season, Semien was again a slightly-below-average hitter. That is seven seasons of Marcus Semien’s hitting registering as passable, but not noteworthy. Seven years of hitting OK…for a shortstop.
And then there is Semien’s 2019 season, when he rated as one of the absolute best hitters in baseball. Over 162 games and 747 plate appearances, Marcus Semies was an utterly different player. His OPS+ was 139, good enough to tie for 9th in the league. His wRC+ was 138. He was – very suddenly - an elite hitter.
Here are those numbers in graph form:
There is no other player in baseball history who can combine that discrepancy with so much playing time. Ozzie Smith was an average-ish hitter who got better, but his OPS+ peaked at 112. Zoilo Versales peaked at 115 during his MVP season in 1965. Luis Aparicio peaked at 114. Chone Figgins peaked at 117 and had another year at 110. Ten percent better than the league average is good, but it doesn’t qualify as elite.
You can find pitchers and part-timers who have nice runs, but it is difficult to find a player who can claim one year of elite hitting against a career of mediocrity.
What’s more interesting is that Semien’s statistical record doesn’t lend any very obvious reason for it. We might expect that Semien got incredibly lucky in 2019, but he didn’t have extraordinary luck on balls in play: his BABIP was .294 during his breakout season, .291 for his career). He also didn’t change parks or teams: he didn’t find himself thriving in a new environment or under new coaching.
The substinative change – using the word ‘substantive’ loosely – is that Semien’s walk rate got a little better, and he struck out a little less often. But even that doesn’t explain how his hitter suddenly paralleled J.D. Martinez. His exit velocity increased slightly, and he ‘barreled’ more balls (7.4% from a career average of 5.1%), but he reduced his launch angle on balls-in-play. His groundball-to-flyball ratio was unchanged, his pull/opposite rate was neutral, and his line drives actually decreased a bit. His discipline on pitches didn’t change he swung at the same percentage of pitches outside the zone and in the zone, and he made contact at the same rate as previous years. Pitchers threw him the same assortment of pitches, at the same velocity, and balls left his bat at the same speed.
Framing all of that differently: if you started by looking at the very insider-baseball, balls-in-play metrics that are far down on his FanGraphs page, you wouldn’t expect to see the dramatic difference between the Marcus Semien who played in 2019, and the Marcus Semien of 2013-2018, or 2020.
But the difference is there on the first page of statistics: Semien had a full year where he was an elite major league hitter.
So what can we expect going forward?
Broadly, there are two possibilities. One is the Semien’s 2019 season was a fluke, not discernible in the underlying metrics but an outlier campaign all the same.
The other possibility is that you can’t fake a full year with a 138 OPS+: it is a marker of ability that will show up again.
A player who is an interesting comparable to Semien - one player that might support the Blue Jays gamble - is future Hall-of-Famer Adrian Beltre.
Beltre had a career OPS+ of just 97 before his epic walk-year for the Dodgers in 2004. He followed that with a dud first year in Seattle, and didn’t really get back on his feet as an elite hitter until he signed with Boston as a thirty-one year old.
Let’s compare them:
Beltre OPS+
Semien OPS+
Beltre was younger than Semien: he was nineteen when he debuted in the majors, whereas Semien was twenty-two years old. And Beltre’s breakout season was massive: 48 homeruns, 200 hits, an OPS over 1.000. Semien’s 2019 season was terrific, but it wasn’t as eye-popping as Beltre’s breakout.
So what is it going to be?
FanGraphs has five projections for Semien posted so far, and his anticipated wRC+ ranges from 102 to 117. Two projections suggest he’ll be back around 100, while three split the difference between peak Semien and rest-of-his-career Semein.   
Marcus Semien is one of the players I’m most interested in watching in 2021, because I don’t know what the answer is. Either we’re going to understand his 2019 season at one of the most unusual one-offs in baseball history, or his hit tool is going to show up again at some point.
What are you betting?
David Fleming is a writer living in southwest Virginia. He welcomes comments, questions, and suggestions here and at

COMMENTS (8 Comments, most recent shown first)

Hi Dave,

Point well taken on 2020 and I have used the same argument (when it forwards my position).

I thought it was relevant because 2020, while not extensively mentioned in your article, was extensively mentioned in the comments as a harbinger of a return to mediocrity by Marcus.

However, seeing as this was the first two weeks of this weird season, after a layoff and preseason unique in baseball history, I though it worth a mention.

And, Mr. Fleming, if that is your name, I will carry that assertion to the grave. Good day, sir!
11:05 PM Mar 1st
I'd be wary of chopping off bits from a fifty-game season and saying they showed something significant, OBS2.0, though I've seen a few other folks make the same point you're making.

We could just as easily find a bad spell from Semien's 2019 season which, if removed from the rest of the season, would spike his OPS to .910-.920. And an OPS of .763 is a lot closer to his career average than his 2019 outlier season.

I'm still curious what people think: does that hit tool show up again, or was it a fluke?

I suppose I should cast my vote: I think it shows up again: I think if Marcus keeps playing in the majors, he'll have another year with an OPS+ in the 125-145 range.
10:18 AM Mar 1st
Fwiw, Semien had sort of a two part 2020. Two weeks in he was hitting .179 with an OPS in the 4s. The rest of the way his OPS was .763, which would have been more than 30 points above his best season save 2019.
2:49 AM Feb 28th
I spent 10 minutes looking up. guys who had an unbelievable year mid career to see if I can find a parallel to Semien. Haven’t found one yeat. Elliott Maddox, 1974, comes close. I looked at Petrocelli, Finley, Kevin Elster (don’t laugh; look at his 1996 - 24 HR, 99 RBI) - no one like Semien.
11:09 PM Feb 26th
For what it's worth, Semien made a similar jump between his last college season at Cal (in 2011) and his first AA/AAA season two years later (in 2013):

2011 at Cal: 61 games; .275/.371/.415 w/ 5 HR

2013 AA/AAA: 137 games; .284/.401/.479 w/ 19 HR

Accounting for more games played in 2013 than 2011, specifically 2.25 more games, he would have hit about 11 HR in 2011 had he played in 137 games. So, 11 HR w/ an aluminum bat and lesser competition v. 19 HR w/ a wood bat and better competition. And 2011 was pre-BBCOR aluminum bats, so, in college, he benefited from using the juiced BSR bats - for perspective, going from a BSR aluminum bat to a wood bat is like going from a tennis racket to a ping pong paddle. Seems something clicked at AA/AAA in 2013.

Not only is this a significant jump in performance, it's an even bigger jump in competition. Granted, in the minors, he likely put on more muscle and had better coaching (or, at least, more individual coaching; probably only had 2 coaches w/ a grad assistant in college).

It doesn't necessarily explain the phenomenon you described above, but I think it's relevant.

Food for thought.
12:20 PM Feb 26th
My view, Bear, is that if you can post an OPS+ of 112 in the major leagues at twenty-on e, it's not thatsurprising that you'd post a 148 OPS+ a couple years later.

Ketel has certainly had a weird, rollercoaster career, but it doesn't parallel Semien. Marcus established a baseline as a slightly-below average hitter for six years, and then broke out suddenly. Ketel has been all over the map.

Phrasing it differently: you can sort of 'see' the story of Ketel. A skillful young hitter got the call and did well in a short rookie year, mashing fastballs and feeling good about it. The pitchers realized he could catch their hard stuff and went to work figuring out his weaknesses. The book on Ketel went out, and he struggled for a couple years, humbled and learning the secondary stuff about hitter. He learned and grew into his skills...'skills' became 'talent' and he reached a higher peak.

That happens all the time in baseball: there are plenty of Ketels. The Reds outfielder Aquino might be a Ketel. I'd bet that Houston slugger Yordan struggles a bit this year. It happens a lot.

It does NOT happen that a player has five or six years of steady, mediocre hitting, and then manages a year where he hits like Mookie Betts.

10:13 AM Feb 26th
Dave, I think there is more players like Semien in that group. The season was short last year and we don't know if last year was a change in skill or a fluke because of 50 games played. I think Ketel Marte is a similar boat to Semien. His OPS plus for his career: 112, 68, 88, 102, 148, 98.

He played 100 games in years 2, 5 and 6. He was 26 last year. Was 2019 or 2020 a fluke. He showed an increase in power in 2018 and another in 2019. His walks didn't increase in percentage of at bats from 2017. Last year he walked only 7 times in 195 plate appearances.

8:15 PM Feb 25th
Hey Dave!

Marcus credits his year to changing from a 34 to a 33.5 bat. But, of course, he reverted to normal in 2020.

All I can think is that the new bat changed his tendencies, which he basically references, and that in 2020 the book caught up on him.

So, I'll bet he is back to the OPS+ 80s guy.

Be well!
4:33 PM Feb 25th
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