The Mariners 2013 Starting Rotation is Fine

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Forced to predict the 2013 Mariners Opening Day rotation, I would not expect any of Danny Hultzen, James Paxton or Taijuan Walker to be among the first five. Similarly, I doubt that an Andrew Carraway or even Hector Noesi is a first choice either. I expect that Felix Hernandez, Jason Vargas and Erasmo Ramirez will have spots unless something highly unexpected happens. Erasmo might be a stretch but I don't see a reason to keep him out.

Outside of those three, the picture is far murkier. Among players that will be property of the Mariners next season, it probably goes Blake Beavan and then Hector Noesi. I don't anticipate that happening however. I believe the Mariners will make a sincere push to retain Hisashi Iwakuma and likely pursue next year's version of this year's Kevin Millwood. Perhaps they'll aim higher and go after someone like Brandon McCarthy or Edwin Jackson, but my interest in this piece is limited to a more conservative scenario.

For the sake of this post, I'm going to assume that the rotation that breaks camp is Felix, Vargas, Iwakuma, Erasmo and Beavan. Of course, the rotation will likely change as the season goes on. There'll be depth down in Tacoma ready to step in if needed and prospects pushing their way up either there or starting with a repeat in Jackson that may arrive in Seattle next season. Again, that's not my concern right now. What I was curious about is assuming the above five starters, how good of a rotation is that, actually?

The overall sentiment in yesterday's recap thread where this was broached was not positive. I wanted data though so as a spot check, I looked at three numbers* first before applying any subjective analysis: 2012 xFIP, 2012 TRA and ZiPS "rest of season" FIP.

* Note: numbers compiled before Tuesday's games.

xFIP

For those unaware, the full formula for xFIP is:

xFIP = (13*FB%*League-average HR/FB rate + 3*(BB + HBP) - 2*K) / IP + constant

xFIP is FIP with the actual home runs replaced by an expectation for home runs based on a pitcher's fly ball rate. We can do better than that, but it's a useful stat and among the first that I always check for pitchers. A league average xFIP for a Seattle Mariners starter (that is, correcting for Safeco's influence) would require about a 4.16 figure. So far this season, the xFIPs for the five starters in question are:

Felix Hernandez: 3.28
Jason Vargas: 4.45
Hisashi Iwakuma: 3.92
Erasmo Ramirez: 3.73
Blake Beavan: 4.92

Those average out to 4.06, a number that's better than average, but a straight average is too simplistic. We know Felix is going to get a preferential load of starts and will pitch more innings. So I tweaked it by weighting each pitcher's number by a hypothetical inning count of 230 for Felix, 175 for Beavan and 195 for the other three. That 990 IP total is about average for an AL team. That pushed the rotation's combined xFIP down to 4.02, or about 16 runs better than average over the course of the season.

TRA

TRA is a more complex version of FIP. It assigns values to batted ball types as well as strikeouts, walks and home runs. It does not have a regression of home run rate like xFIP does though so in case you think that Vargas and/or Iwakuma get too much credit from xFIP using league average HR/FB rate, TRA doesn't have that problem. A league average TRA (again, park corrected) is 4.68 this season. And here are the five Mariners:

Felix Hernandez: 3.54
Jason Vargas: 5.17
Hisashi Iwakuma: 5.09
Erasmo Ramirez: 3.61
Blake Beavan: 4.88

You can see the big jump on Vargas and Iwakuma that come from their high home run rates this year. Nevertheless, without any adjustment, these five TRAs, weighted as above, come to a total TRA of 4.42, or about 29 runs better than league average. That shouldn't actually be a surprise since the Mariners' rotation currently ranks above average according to TRA and while that's with Kevin Millwood's positive contribution that's also with Hector Noesi's far bigger negative one.

Using 2012 xFIP and TRA isn't quite a projection for 2013 of course. Those are both measurements of how the pitchers have performed, not systems designed to project how they will perform. However, I don't think anyone would consider it a stretch to use either as a baseline for future performance. Still, I decided to look at one specifically meant to be a projection.

FIP

As you might have guessed from xFIP, FIP is:

FIP = (13*HR + 3*(BB + HBP) - 2*K) / IP + constant

FIP is a more basic version of TRA and so I didn't bother to use 2012 FIP as a check. Instead, I wanted to introduce a bit of projecting by using ZiPS FIP number for the rest of the season. I think it's reasonable to assume that what ZiPS feels each pitcher should do in these final two weeks is going to be fairly similar to what it'll think each pitcher should do in 2013 since none of these rotation candidates are especially at risk for age-related decline. That is also why I felt fine using TRA and xFIP above; for these five pitchers, their 2012 performance is probably a decent guide for what we're going to expect from their 2013s.

A league average FIP (adjusted down for Safeco) is 3.89 this season. And here are the five Mariners:

Felix Hernandez: 2.75
Jason Vargas: 4.22
Hisashi Iwakuma: 3.74
Erasmo Ramirez: 4.43
Blake Beavan: 4.60

The drops for Vargas and Iwakuma re-appear as their home run proclivity gets regressed again. Erasmo gets his worst rating yet, mostly due to the skepticism ZiPS takes toward rookies. Still, these five combined come to 3.89, exactly average.

So three measures, all worthwhile I believe, come in with that rotation being above average, well above average and exactly average. What gives? On name value, it does seem like that rotation is not exactly inspiring, but on aggregate, it seems fine.

A big point in evaluating the rotations is that Felix Hernandez is really, really good. His grace provides a lot of slack for the rest of the rotation and in truth, none of the other four are all that poor. People tend to overestimate how good the back of a rotation is in reality. About four years ago I wrote this piece looking at how pitching performances actually split out by rotation slots. I just re-ran the same process and things haven't changed much at all and the main point still applies. You can bemoan Blake Beavan or Jason Vargas as near replacement level, but I think that's not true. Their ability to perform at their (this year) mediocre level over lots of innings is valuable in keeping those innings away from people like Hector Noesi or Tommy Hunter.

Furthermore, a quick point specifically about those two is that both Beavan and Vargas have a history of getting more than an average share of infield pop ups. Those aren't as flashy, nor are they as stable as strikeout rate, but they aren't random either and results-wise, an infield fly is just about as good as a strikeout. If there was a measurement that combined xFIP's home run regression and TRA's batted ball values, which I think would be reasonable, these guys might look better still.

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