How much can Athletics infielder Marcus Semien improve?

A reader recently asked for an updated take on Oakland Athletics shortstop Marcus Semien. Through 136 games, the 24 year old infielder is hitting .257/.303/.390 with 22 doubles, 11 homers, 11 steals, 33 walks, and 112 strikeouts in 487 at-bats. His wRC+ isn't bad for a shortstop at 93, but the advanced metrics don't like his defense much and ultimately he parses out at 1.0 fWAR.

His 2014 season is very similar to what he did last year with the White Sox: .234/.300/.372, wRC+90, 0.5 fWAR in half the playing time. Overall Semien is better than a replacement player but his performance isn't enough to guarantee him a permanent job at this point.

Can that change?

First, this is the analysis for Semien from my 2014 book after he hit .284/.401/.479 with 19 homers, 98 walks, and 24 steals in the high minors in 2013:

I had Marcus Semien rated as a Sleeper Alert! pick entering 2013 and I’m sure glad I did. He had an excellent season showing a fine power/speed combination and first- rate plate discipline in the minors. Between Birmingham and Charlotte, he produced an outstanding .420 SEC, showing a very broad set of offensive abilities. It is true that he had some contact problems during his 21-game major league trial, but with his track record I think he’ll figure it out given more adjustment time. Semien’s defensive tools fit best at second base, but he’s not a terrible shortstop and can fill a spot at third if necessary. I like him and while he shouldn’t be expected to be a .300 hitter, I think he is for real and should help his team win in many ways. He was a great find as a sixth-round pick (2011, University of California). Grade B.

With a year and a half in the majors under his belt, that is still pretty much what I think.

Although used as a shortstop by Oakland he seems a more natural fit at second base and the advanced metrics agree. He hasn't shown the same level of plate discipline and on-base ability in the majors as he did in the minors, but his whiff rate has declined this year without significant loss of isolated power, which is a good sign.

There's an old adage that if a young player showed a skill in the past, he owns it; it is still in there somewhere, even if he needs time to manifest it against the best competition. It doesn't always work out that way of course, but the younger the player, the more likely it is to happen. Semien is still reasonably young at age 24. There's a reasonable chance that his plate discipline will sharpen up and the OBP rise.

The updated take: he belongs at second base, and the bat will likely improve further. I still don't see him as a .300 hitter, but can he hit .260 with a better OBP than he's shown so far, with more power than typical for the middle infield and being a solid regular overall? Yes, I think that can and will still happen.