What's up with Corbin?

Don't worry about the Nats loss last night.  They still won the series as far as I'm concerned and their run has gone like this

Marlins series at home? Won.
Mini-series at Atlanta? Won.
Cincy series away? Won.
Split Chicago home and home? Won.
Padres series away? Split.

Like I said they had one split afforded to them. One split is all they have so far. Now comes the Diamondbacks at home. Win this, go 3-1, and they've done exactly what they should have going into the Phillies and Braves series that will likely decide whether there really is a season remaining or if it's just a team playing out the string.

The Nats offense is humming. The Nats back of rotation and bullpen are doing well enough. But remember that one of the keys to the Nats making a comeback was the Top 3 pitching like the Top 3.  One guy hasn't done this. Corbin has now had three poor games in a row and while you see people pointing to the Marlins complete game as a possible turning point (too many pitches I guess?) the fact is he had a bad start before that as well, putting nine Mets on and giving up two homers in just 5 innings. Is there something we can note about what's going on?

1) He's become way more homer prone. In those 4 games (skipping the Marlins one) Corbin has given up 6 homers in 17 and 2/3rds innings. That's about 3 homers every nine which is... quite bad. Part of that is a GB rate that isn't as good as it was to start the year. As well he's getting hit harder. Simple enough equation to work out here.

2) He's kind of walking more and striking out less. Kind of. You know it's five games and there isn't an OMG thing here. Just a vague general trend that suggest he doesn't have his best stuff.

3) He's getting hammered when he puts men on. This is one of those stats that is hard to decipher. Could be that he's messing up somehow when guys get on base. Too distracted? Too much focus? Could be just some dumb luck not going his way.

4) He's had some bad BABIP days.  That Cincinnati game was fluky bad for BABIP. Almost .600 which likely mean a handful of seeing eye hits all getting through. Other games aren't as bad and more go along with the - just getting hit harder so there are more hits.

There's no super telling thing here. The first point is the most telling - hit harder and more balls in the air - and after that there's a mish-mosh of things that might matter, might be artifacts of Corbin adjusting for the first point, or might be bad luck.

Has he changed his pitching? He seems to think his issue is fastball location, which helps negate the effectiveness of his slider. Maybe he's throwing a couple fewer sliders for a couple more changes and curves.  But he's basically maintaining how he pitched before in terms of hards/changes. He notes that as far as the "hards" go, he's going more with sinkers recently but it isn't working the same as the sinker is usually a pitch you pitch to be chased down in zone but are also ok if it gets hit (since it induces GBs). Fancy stats agree that his fastball and slider have been ineffective, and less effective lately (Other pitches - which are thrown like 10-15% of the time are stable). Fancy stats also do agree he's hitting the zone less now than earlier in the year and batters are making more contact, both in and out of zone.  And fancy pitch specific stats show that while the slider is consistent, his fastball has more horizontal movement (which could indicate less control) and is finding itself more in to batter than it has all this year (and last mind you) and looking at hard pitches exactly you see far fewer in the zone recently.

To summarize that last paragraph - he seems to be on it.

Corbin isn't able to locate his fastball. I'm going to assume he is falling behind early (i could dig into counts to find out for sure but I don't have unlimited time people!) and so batters are more likely to lay off a suspected slider. He can adjust with more sinkers but that's only going to work if he can locate the sinker in a way I suspect he hasn't tried before - nailing the bottom of the zone. If batters aren't aggressive then he's still going to fall behind. (This is probably why he still did well in that Marlins game - they an aggressive team who also don't work walks) Then they can wait for a good pitch. It may not come but if 7 batters for every 9 gets to wait for two pitches, instead of say 3 - well you see the difference.

Is there any adjustment he can make? Probaby not. He doesn't seem to pitch the slider or sinker to get called strikes, using the fastball for that. Nor does anything but the horizontal movement of the fastball seem to have changed. If it were slower, if other things had changed, you might try to look for something bigger to fix. For this we're left with trying to watch him figure it out what minor tweak is needed to get that one thing back on track.