Does any free agent represent the unpredictable and difficult-to-interpret 2020 season more than shortstop Marcus Semien? Here are the twists and turns that teams have to consider when evaluating Semien on this winter’s market:

He’s among the most valuable free agents available
In fact, the most valuable, if one lumps together each free agent’s 2019-20 FanGraphs Wins Above Replacement (WAR) totals to account for the abbreviated ‘20 season as we did on MLB.com’s master list of free agents here. Semien has accrued 8.8 fWAR since the start of ‘19, followed by George Springer (8.4), DJ LeMahieu (7.8) and J.T Realmuto (7.4).

But, if you followed Semien and the A’s this season, you’re likely aware that …

Much of that WAR total is built from 2019
Semien’s 1.2 fWAR in 2020 tied for 17th among shortstops, and if one employs the shorthand version of MLB.com senior data architect Tom Tango’s method for translating 2020 WAR to mirror that of a normal season, Semien would have finished somewhere around a pedestrian 2.5 total. That's obviously a huge step back from the 7.6 fWAR that made him an American League MVP Award finalist a year ago.

Semien’s offense took a hit, regressing from a .285/.369/.522 slash line in 2019 to .223/.305/.374 in ‘20. That represented one of the 25 biggest drops in OPS among players who logged at least 150 plate appearances in both seasons. But perhaps even the bigger concern is that …

Semien’s defensive gains slipped away
Much of Semien’s 2019 was built upon the massive improvements he made with his glove. The A’s shortstop went one from one of the bigger liabilities in the game to a standout at the position, tying Willy Adames and the great Andrelton Simmons for fifth among full-time shortstops with 12 defensive runs saved (DRS).

That work at a premium defensive position, paired with a breakout season with the bat, is what catapulted Semien into the AL MVP conversation. But he dropped all the way to -5 DRS in ‘20, ranking among the very worst full-time shortstops. General managers must take that drop-off with a large grain of salt, of course, because 60 games are not enough for complex fielding metrics to stabilize and become predictive. Making matters even more confusing with Semien is that Statcast’s Outs Above Average (OAA) metric (which, unlike other major defensive metrics, tracks exactly where a fielder stands to account for shifts) actually rated him as a below-average defender in both 2019 and ‘20. For those that prefer the old-school statistics, Semien made more than half as many errors (seven) across 451 innings at shortstop this year as he did across more than 1,400 innings (12 errors) in ‘19. 

So Semien regressed in both facets of the game, but how much of that was related to …

Injuries that held him back
Semien has long been a mainstay in the A’s lineup, but his string of 276 consecutive starts (the second-longest streak in Oakland history) was snapped in early September because of lingering soreness in his left side. The injury reportedly made it difficult for Semien to swing the bat, and he admitted then that his “strength wasn’t there” and he “didn’t feel great” while powering through the first leg of a doubleheader against the Astros on Aug. 29.

“I’m the type of guy that tries to grind through things, and in the past things have just gone away,” Semien told the San Francisco Chronicle. “But this one was a little bit more intense. It sucks, because these are important games I want to be a part of. But the most important thing is getting back healthy for the end of this season and making sure it’s not something that can get worse.”

Semien didn’t play much better after a nine-day rest, slashing just .211/.341/.366 across his last 20 games. But then, just to throw one more wrinkle in there …

He mashed in the postseason
Semien’s bat came to life beginning with the A’s Wild Card Series matchup against the White Sox, which saw him homer in Game 2 and then go 2-for-4 with a double in Oakland’s decisive Game 3 victory. He was even better in the A’s ALDS loss to the Astros, going 8-for-14 (.533) with a homer, two RBIs and a 1.344 OPS across Oakland’s four-game defeat.

But even setting aside the extremely small sample size, how much of Semien’s explosion was tied into how the ball was carrying at Dodger Stadium? The A’s and Astros combined to belt 24 homers in just four games, breaking a 25-year-old Division Series record. And for all the offense, Semien’s defensive troubles cropped up again when he committed an error that was a factor in Oakland's series-opening loss.

So where does Semien go from here?

Semien is only 12 months removed from being considered one of the AL’s best players. But 2019 also stands as his only season with an above-average OPS+ and one of just two (along with ‘18), in which several major defensive metrics agreed that he was well above average with his glove. A Bay Area native, Semien likely fits best with his hometown club, particularly given his standing in both the clubhouse and in the Oakland community. But it’s unclear how much the A’s will spend, especially after they chose not to extend qualifying offers to both Semien and closer Liam Hendriks.

Entering free agency without that qualifying offer theoretically makes Semien a more attractive option, but both MLB Trade Rumors and FanGraphs’ free-agent prediction lists believe he will sign for an average annual value that falls below the offer’s $18.9 million standard. Plus, fellow shortstops Didi Gregorius and Andrelton Simmons are also free agents this offseason, and teams might be more inclined to wait for next year’s historic free-agent class that could include Javier Báez, Carlos Correa, Francisco Lindor, Corey Seager and Trevor Story.

Coming off a down performance amid the trickiest of seasons to evaluate, the conventional wisdom says that Semien should look for the best one-year deal he can and use 2021 as a springboard for his next free-agency venture. But with that super-shortstop class looming next winter, maybe Semien would be better served looking for a longer-term home. His agent, Joel Wolfe, remains confident that Semien will cash in this winter.

“We haven’t seen a premier free-agent shortstop anywhere near Marcus’ age or skill level for a very long time,” Wolfe told The San Francisco Chronicle this week. “We’ve always viewed Marcus as a $100 million-plus player. His pure value in the industry is north of $100 million.”

Whether the industry agrees remains to be seen.