Gotta worry about Darvish, He throws a lot of pitches and seems to want to strike everyone out. No 3.48 is not a sky high ERA, but seems like when they get on they usually score.
But... it's spring training. Pitchers work on their various pitches in ST, they're not out there in competition mode, usually. It's a credit to just how phenomenal Darvish's stuff is, that he's getting a ton of K's while not really working on throwing the *right* pitch -- just working on throwing a given pitch as well as he can. Or just get that mythical "feel" for it.
That said, Darvish is quoted as having been mostly interested in standing out somehow when he first came to MLB, feeling like he was the "face" of Japanese baseball in MLB at that time. Since he didn't have a killer 100+ fastball, he decided to try and strike out every batter he faced by developing a *lot* of pitches.
He succeeded, and to an extent, yeah -- he does try to strike out everyone, even during ST. But also, the guy has like eight pitches... if he spent one ST start working on the "feel" of each, I think that's more ST appearances than he's likely to make, period.
So, again -- not a lot to take away from ST, otherwise known as Small Sample Size Theatre, except for ensuring physicality looks and feels good across the board, and no one is showing signs of any bad injury or medical issues. Even pitchers showing control issues, unless in context with a history of same, don't bother me much; if you spend a few innings, like Chatwood did a few days ago, working on getting your cutter over the plate (and failing), of course your control isn't gonna look good. But during the season, he'd have swiveled to pitches he was locating better.
So, yeah... not much to worry about, here, I don't think. The biggest surprise takeaway thus far is the Cubs appear to be considering going north with only 12 pitchers. THAT would be a front-page story, knowing Maddon...