And although he has shown flashes of brilliance, Arrieta has been dealing with one major problem: walks. In fact, he has more walks (46) than strikeouts (39), and he has walked at least two batters in each of his 15 starts. That is not a good sign.
In the minors, Arrieta did walk his fair share of batters, but not at the rate he is right now. Here's his strikeout and walk rates from his time in Frederick, Bowie, Norfolk, and Baltimore:
Now, much of that difference in Baltimore can be attributed to simply facing better hitters who won't chase as many pitches out of the zone. But why did Arrieta start walking almost a batter more per game at Norfolk when he was 24 instead of 23? Sure, it's not a big innings sample size, but it's still a bit odd, especially considering that his strikeout rate essentially stayed the same.
So what's the problem? Is Arrieta nibbling too much? Does he not trust his stuff enough to finish hitters off? Or is he just getting used to facing major league hitters who won't swing at pitches that many minor leaguers go after? It's probably a combination of all three, and it may be worth exploring if Arrieta's still struggling with his command next season. Right now, I think Arrieta deserves the benefit of the doubt because, after all, he's only thrown 83 major league innings. However, it's difficult enough to pitch effectively in the majors without walking nearly five batters per nine innings. Hopefully Arrieta makes the necessary improvements in the near future and pitches more efficiently in the zone.