Oakland's Marcus Semien's Defense Could Be Historically Bad

There is no denying that the trend in baseball has been to favor the pitchers and defense at the expense of offense. Defense is more highly valued now than perhaps ever before, with defensive shifts all the rage and defensive sabermetric stats all aiming to give teams a better understanding of just how important run prevention is.

Teams are less reluctant than ever to put a below-average defender in the field, unless he is so valuable offensively that there is just no way to keep him off of it.

Which brings us to the interesting case of Oakland A's shortstop Marcus Semien.

On Thursday, Semien committed an error that led to two unearned runs in the Yankees' 6-2 win over Oakland. That was his 28th error of the season, eight more than the next closest player, Washington shortstop Ian Desmond. That's six errors fewer than the Los Angeles Dodgers have made as a team.

And with 88 games now in the books for the A's, that puts Semien on pace to commit a mind-boggling 51.5 errors this season. That would be the most errors in a single season since 1950, when Chicago Cubs shortstop Roy Smalley committed 51 errors in 154 games. Smalley was a power-hitting shortstop that season, which explains why he was permitted to commit those 51 errors, hitting .230/.297/.413 with an OPS+ of 85, 21 homers, 21 doubles, 85 RBI and a league-worst 114 strikeouts.

While Semien isn't hitting for that kind of power, he's been a slightly better hitter than Smalley was in 1950, with a slash line of .258/.304/.401 with 8 home runs, 34 runs scored and 7 stolen bases. However, he's also a high strikeout guy, with 75 in 346 plate appearances.

If Semien's errors continue at this rate, it would be a drastic increase over the league leaders in baseball over the last 10 years.

The most anyone has had since the 2005 season is 34, done twice, by Mark Reynolds in 2008 (at third base) and Desmond in 2010 (at shortstop).

However, errors are not the only stat we go by when judging someone's defensive prowess, or lack thereof.

According to Fangraphs' defensive statistics, Semien has actually been worth one defensive run saved (DRS), a surprising number given all his errors. His OOZ of 45 (outside of zone), meaning the number of plays he made that were judged to be outside the zone of an average shortstop, was eighth-most among MLB shortstops. That means he gets to more balls than most. And his RngR (Range Runs) of 3.0 indicates he has saved three runs over the course of a season based on his range alone.

However, his UZR/150 (ultimate zone rating), which encompasses all these numbers, plus a few others, is -14.2, meaning he's cost his team 14.2 runs over the course of the season with his poor defense. Only Desmond has a worse figure among shortstops, and that was before Semien made his 28th error on Thursday.

Of course, the most important thing is whether or not Semien is actually costing his team wins by playing such poor defense. ESPN's Dave Schoenfield, with the help of Baseball Info Solutions, found that the A's are actually one gave over .500 (12-11) in the 23 games in which Semien had committed an error coming into Thursday (that record fell to 12-12 with the A's loss to the Yankees). His 28 errors have led to just 11 unearned runs, and Schoenfield noted there has really only been one game this year in which a Semien error tangibly cost his team the game.

Whatever you think of Semien's defense, at least this much is true: if he continues to pile up errors at his current pace, he is going to cost the A's some games somewhere down the road here in 2015.

And he might make some history in the process.