The most popular narrative surrounding the 2015 Orioles decline is that the offense is good but the pitching seems to have gotten worse since last year. Is this true? I continue looking at how the 2014 Orioles became the 2015 Orioles by examining the rotation. Part one, which examines, the offense, is here.

Let’s look at Fielding Independent Pitching (FIP) first. Actually, let’s quickly adjust for park and league by looking at FIP- for the starting rotation, where 100 is league-average and lower is better.

2014: 107

2015: 111

Okay, there is a decline there, relative to the league, of 4%. That’s not insignificant. Where is the decline in FIP coming from? It's not in strikeouts or walks; the starters' K-BB% has actually improved since last year:

2014: 10.4%

2015: 11%

This must mean the starters are giving up more dingers. And indeed they are. Here is HR/9-, which is the team HR/9 rate relative to the league rate. Again, 100 is average and lower is better:

2014: 113

2015: 127

There has been a league-wide increase in starters giving up gopher balls, but not to the extent that the Orioles starters are. Yowza.

But remember that home runs involve some luck as well, on a per-fly-ball basis. Interestingly, the starters' fly ball rate has decreased since last year:

2014: 38.1%

2015: 35.5%

Huh, that's weird. If the pitchers are giving up fewer fly balls, I would expect there to be actually fewer home runs. Instead, there are more home runs. This smells like regression to the mean or perhaps bad luck. And indeed, if we look at xFIP-, that seems to be the case. xFIP- normalizes HR/FB rate to league average, stripping out random fluctuations in said rate, while also adjusting for park and league and indexing to 100.

2014: 109

2015: 106

The rotation's xFIP has improved, relative to their park and league. Now we can say that the increase in home run rate, while scoring literal runs against the team, should not be blamed solely on the pitchers. As a case study, look at Kevin Gausman, whose regression to the mean has morphed into simple bad luck as his HR/FB has climbed from 5.8% last year to a cringe-worthy 13.9% this year.

FIP and xFIP tell us something about where the extra runs are coming from and maybe whom should be blamed for them. But the biggest indicator of the team's decline by far is the rotation's ERA-FIP differential. Last year this differential was a staggering 60 runs. That’s about six full wins and would’ve taken the team from 96 wins to 90, from a division championship to maybe just fighting for a Wild Card spot.

This year the differential is two runs. Yes, two, you read that right. From six wins down to less-than-half a win. Visually:

Yeah. See that giant gap from year-to-year? That's the pain and frustration of more runs crossing the plate while an Orioles starting pitcher is on the mound.

The main culprits on the staff are the ones you'd expect. Year-over-year ERA-FIP changes (where an increase signifies more runs crossing the plate than expected):

The remaining starters have seen their ERA-FIP gap get better, but not enough to offset the huge losses posted by these three pitchers.

Ah, 2014 Miguel Gonzalez. We hardly knew ye.

Now, ERA-FIP differential is not a cause by itself. It’s an indicator that more runs are scoring against starters than fans should expect, given said starters strikeout, walk, and home run rates. Actually, wait. Specifically for the 2015 Orioles, it’s an indication that the 2014 rotation was unsustainably good, and that the 2015 rotation is allowing exactly as many runs as fans would expect.

Let’s dig into possible causes of run inflation for each of these three pitchers. As I showed earlier, pretty much the whole staff across the board is giving up more home runs than they were last year. Besides that, each guy has some particular areas of note.

Tillman is striking out fewer batters than last year and walking more, leading to an anemic K-BB% rate of 7.9%. For context, a league-average starter this year has a K-BB% of 12.2% and higher is better. His strikeout rate has dropped by one percentage point while his walk rate has risen by 0.7 percentage points. This is the third straight year his strikeout rate has declined.

Gonzalez is simply giving up more home runs than last year. His K-BB% has actually increased by 0.7 percentage points. Norris, however, stunk. His strikeout rate dropped 3.8 percentage points, a very large decline for just one year. (That's looking at his numbers with the Orioles; since joining the Padres he has been performing much better.) His walk rate remained about the same, but the drop in strikeouts drove his K-BB% down to a measly 8.2%.

In addition to fluctuation in strikeout and walk rates, each of these starters experienced a sharp rise in BABIP against:

Tillman: +.028

Gonzalez: +.020

Norris: +.051

Combined with the rest of the rotation, it looks like this:

For Tillman and Gonzalez, the increase looks like regression to the mean. Their BABIPs were unsustainably low in 2014. Fans should've expected them to rise to the .290-.300 range, and that's what they did. Thus, more runs are crossing the plate against them.

For Norris, however, that sharp rise looks like bad luck. No one would ever predict a BABIP of .330 for a pitcher, but every year a handful of poor souls are victimized by the BABIP dragon; this year, Norris happened to be one of them. He did make matters worse by striking out fewer batters, meaning many more balls were being put in play against him. When you rely, purposefully or not, on hitters making weak contact, all you can do is pray to Jobu that you strand some runners. And that you aren't walking anybody.

You also have to put some faith in your defense, at least, if you had a time machine to travel back to 2014. Because as I showed in my article last week, the team's defensive capabilities have taken a huge hit this year. This decline likely contributed to the rise in BABIP for these three pitchers.

The drop in strikeout rate, giant increase in home run rate, and rise in BABIP (partially brought on by a decline in defensive skill) all explain why the starters are stranding many fewer runners than they did last year. As shown by the LOB% metric, here are the changes in rates:

Remember that a league average LOB% is 72-73%. As Gary Thorne would say, "Mercy". Norris and Tillman were both the recipient of some awful luck (Norris particularly so), while Miguel Gonzalez's strand rate simply regressed to the mean.

Let's put it all together. Here’s how I would frame the 2014-2015 "decline" (scare quotes intentional) in the starting staff. The rotation did get worse, with respect to strikeouts, since 2014. But the majority of the apparent decline is that the 2014 rotation was made to look very good by beneficent fortune and great defense. When these things leave a team, as they are wont to do, the pitching staff looks mortal.

I suspect that this is part of Dan Duquette's plan, or maybe, a situation he is forced to tolerate. He (seemingly) can't pay high-strikeout pitchers to come to Baltimore. And the team hasn't developed one since Erik Bedard (remember him?). The next best thing is to assemble a good defense, hope they can get to the balls that are put in play, try to get your pitchers to stop issuing free passes, and pray to the BABIP gods.

Look out for part 3, an analysis of the 2014-2015 bullpens, coming soon.