|I'm scared shitless just looking at this|
Now, 25.1 innings is a tiny sample size, so we can't draw any conclusions, but we can understand where he has been helped a bit by the luck dragon and where he is doing well all on his own merit.
Pineda had a strikeout-per-9 (K/9) rate of 8.8 over 400+ minor league innings, including a K rate of 11.0 in 62.1 of AAA innings last season. His K/9 right now sits at 7.46, which I actually think is just about perfect for two reasons. One, it's not other-worldly, so it doesn't suggest that a big regression is coming - he's being effective without performing at an unsustainable rate as far as his expected strikeouts go. Second, a K/9 rate of 7.5 is just pretty darn good - so just being objective, you can check the "good" box.
His walk rate (BB/9) was something that was supposed to be a real strength for Pineda as he rarely issued free passes in the minors with a BB/9 rate right around 2 over his 5 seasons but inching up to about 2.4 over his two seasons at AA and AAA. Over his four starts thus far, it stands at 3.20 BB/9 which isn't terrible.
But I worry about two things related to his walks: His batting average on balls in play (BABIP) is .253. In AAA it was .290 and in AA it was .306. League average is right around .300. Yes, better pitchers can have BABIP's in the mid .200's but it takes a lot of luck and some really special stuff to pull it off (for reference, Felix Hernandez's BABIP in his Cy Young season was .263). As his BABIP starts to regress towards the league average, he'll be allowing more baserunners simply because of dumb luck. Secondly, I'm sure there's some research out there that can lend some actual evidence to this, but relative unknown pitchers typically have an advantage over hitters. As hitters start to become more familiar with Pineda and his repertoire it stands to reason that he may start giving up a few more hits. This is why I'd like to see that BB/9 get under control and down into the 2.l0-2.20 per 9 range.
Another thing to watch is this: Right now, he's giving up about 50% fly balls and he's yet to give up a home run. This has a lot to do with why his ERA is 1.78 and his xFIP is 3.99. xFIP is expected fielding independent pitching, which is represented similar to an ERA, but it tries to control for the luck factor. It tends to shed light on whether or not a pitcher is under or over performing the actual on-field performance, or something like that. He's going to give up some longballs. Yeah, he pitches at Safeco which will help, but if he struggles versus anyone it's lefties and Safeco is actually pretty HR-neutral for left handed batters. So it's going to happen, and when it does, all his sparkling stats are going to be dulled a bit.
But, and this is the big finale... he has the fastest average fastball of any starter in baseball right now. And it's really not even close at all:
J. Johnson: 94
And consider that there's a lot of concrete evidence that pitchers throw harder as the season wears on (a lot of that has to do with the weather). He has been pretty much 60% fastball and 30% curveball all year and it's producing a whopping 13.1% swinging strike rate, good for 3rd in all of baseball. His fastball has just been electric and incredibly tough to hit. As long as that holds up, he's going to be very, very good.
So, in sum. Michael Pineda is pretty friggin good. He's been downright dominant so far. He has some work to do with his walks. He is probably not going to have a 1.78 ERA at the end of the season. But he is really making the Mariners look pretty good for letting him start the year in the bigs, and he's a huge piece of any optimism about the Mariners future.