Evaluating Pitchers Changing Teams

C.J. Wilson is headed from the 2011 American League Champs to the 2011 American League West Division Runners-up (somehow, I don’t think they will be raising that last banner in Anaheim any time soon). This has huge implications for the division – the Angels finished 10 games out in 2011, with Wilson producing a WAR of 5.9. Move those 6 wins off the Rangers and put even half of them on the Angels, and you have yourself an awfully tight race.

But there are rather large implications for fantasy owners, as well. Wilson’s ERA, WHIP, K, and Wins — the traditional Roto stats — will all be impacted by the move, as will stats like HR, 2B, 3B, and BB, which impact many leagues, including most ottoneu leagues. There are a few things a fantasy player should look at in evaluating this type of change, and Wilson to LAA presents a unique change where some of the changing factors are easier than normal to isolate. Of course most of you can probably predict that a move to Anaheim will help Wilson’s value, but that isn’t really the point — this is also a chance to look at how to evaluate the impact of a scenery change on a pitcher.

There are four major factors that impact a pitcher’s results after a team change:

  1. 1) Park factors
  2. 2) Defensive backup
  3. 3) Offensive Support
  4. 4) Opposition

We are going to assume, for the time being, that luck doesn’t factor in.

Park Factors
One of the reasons it is easier to analyze this change than many others is that we can effectively ignore all park factors other than Texas and Los Angeles. Let’s use Matt Garza’s move to Chicago last year as a counterpoint. He not only traded half his starts in the Trop for half in the friendly-confines, he also moved about half his road games from the AL East to the NL Central.

Wilson, on the other hand, will play the same number of games (roughly) in each of the other AL parks as he did last year. Yes, he is likely trading a start at Houston for a start at Dodger Stadium, and his other interleague games will differ, but most of his road park factors for the year should be about the same.

But his home park factors – that is a big shift. The Ballpark at Arlington is a hitter’s haven, allowing .4 runs per game more than the average park and an extra HR every two games. Angel Stadium surrenders .16 fewer runs per game and .21 fewer HR per game than average. Comparing the two stadiums, Wilson could be expected to give up .56 fewer runs and .71 fewer HR per home start (a little less, actually, since he won’t pitch all 9 innings in most of those games) in LAA than he did in TEX. The Rangers play 81 games a year in Texas and about 10 a year in LA. those numbers reverse now, shifting 71 games from Arlington to Anaheim. That is no small change.*

We can also see that Wilson should give up far fewer HR (1.5 Park Factor in TEX, .789 in LAA); as well as fewer H, 2B, and 3B. Some of this will be offset by adding 10 road games at Arlington that used to be at Angel Stadium; but because the rest of the schedule the two teams play are effectively the same, we can end the analysis there. Overall, Wilson would benefit greatly from a move to the coast. Pitchers even strike out more batters in Anaheim than they do in Texas.

Defensive Backup
Park factors are not the only thing that will impact Wilson when he moves to the Angels – he will have a very different defense behind him. At first glance, it looks like Wilson will see some additional help from his defense: the Angels were second in the Majors with a 6.7 UZR/150 while the Rangers were a respectable 7th with a UZR/150 of 3.6.

But looking a little closer the difference may not even be that much — and things might even be getting worse. Wilson has had a GB% over 49% the past two years, which doesn’t qualify him as a Derek Lowe-esque danger to grass-dwelling creatures, but does put him just outside the top 20 among all qualified starters over that time frame. And the Angels were not nearly as good at infield defense as the Rangers, particularly up the middle, where Elvis Andrus and Ian Kinsler made arguably the best double play combo in the business. The Angels outfield defense has been stellar the past couple years, and should continue to be quite good, but there is no doubt that more ground balls will find their way through the Los Angeles infield than did the Texas infield. Perhaps this won’t be a huge effect, but it will begin to counteract the impact on runs and hits noted above.

Offensive Support
Offensive Support only matters in leagues that count wins, and this one is a pretty simple analysis in this case. The Rangers 2011 wRC+ was 113; the Angels wRC+ was just 96. This gap may tighten a bit in 2012, as the Angels look for improvements from Mark Trumbo and Mike Trout, plus they apparently signed some big-name free agent 1B, but, even so, I don’t think you will find many people anticipating more runs from the Angels than the Rangers next year. And based on that, a player moving from Texas to California will be less likely to win any given start, and therefore is likely to win fewer games.

Finally, opposition changes when pitchers change teams. And this is an other case where the in-division swap would make this an easy change to analyze.

Again using Garza as the counterpoint, he basically had a totally new slate of opposition, meaning that any analysis would require going game-by-game and team-by-team to figure out how things would change. Moving from Texas to Anaheim, Wilson will basically play the same schedule, save for 19 games vs. Texas that used to be vs. LAA, and 6 games vs. the Dodgers that used to be against the Astros. For Wilson, that should boil down to about four starts vs. Texas and 1 against the Dodgers. And, like the park factors, this is no small change.

With the Rangers scoring about .7 R/G more than the Angels and the Dodgers scoring about .3 more than the Astros, those 5 starts could add more than 3 runs to Wilson’s total on the season. That would be .12 in additional ERA assuming the 223.1 IP Wilson had last year. This is not enough to completely counteract the impact of the park effects Wilson will benefit from, but it does make a difference.

What does this all mean for fantasy players? Well, it depends what stats you use. Park Factors will help his ERA, WHIP, K, and XBH. The defense behind him will likely hurt the first two but help with XBH as well (thanks to the improved OF defense). His offensive support with hurt his Wins. And his opposition should hurt just about everything. The park factors should be the biggest impact, so I would expect Wilson to be more valuable, especially in leagues like ottoneu 4×4 or FanGraphs Linear Weights Points leagues, where wins don’t factor in.

Of course, this is probably pretty obvious to most people, but the real point is that this is a good formula for evaluating these types of moves.

*Park factors are from ESPN.com, but could easily be replaced by any park factor of your choosing.

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Chad Young is a product manager at Amazon by day and a baseball writer (RotoGraphs, Let's Go Tribe), sports fan and digital enthusiast at all times. Follow him on Twitter @chadyoung.

6 Responses to “Evaluating Pitchers Changing Teams”

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  1. GotHeem says:

    Can you recommend a good website that compares park factors on a spreadsheet from year to year as well as sortable stats on how they effect 2B, 3B and HR rates?

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    • Jacob Smith says:

      Statcorner is one of the better sites for park effects, but I’m not sure if they have them in spreadsheet format. Overall, the Angel’s stadium decreases offense by about 2%, while Texas increases it by about 6%, if you’re using wOBA. 99/98 and 103/107 wOBA park factors if you want to break it up by handedness.

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  2. sausagemcbiscuit says:

    Wasn’t Kendrick rated pretty highly by nearly every defensive metric this past year? From watching the games, he looked like he easily had his best defensive season

    Callaspo was also excellent at 3B which is good for a lefty starter. Aybar has great range as well. I’m not so sure the IF defense is that much worse in Anaheim. Facing Texas rather than the Halos is the biggest factor here going forward

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    • Chad Young says:

      Biggest factor will likely be the park factors – Texas is just such a great park for offense. But you may be right on the infield defense. The Rangers were better at SS and 2B last year, but worse at 1B and 3B. Overall, it may be closer than I suggested.

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  3. DLowe says:

    One important factor that the author neglected to mention is that Wilson goes from a #1 pitcher in Texas (facing other teams’ #1’s) to a likely #3 in Anaheim (behind Weaver and Haren) and maybe even a #4 (behind Santana), so the pitchers that he will face on other teams will be of lesser quality. This should help his run support and therefore his wins, balancing out anything he loses in line-up based run support moving from Texas to Anaheim.

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    • Chad Young says:

      Don’t think this is a real factor. After the first week or two, teams rotations rarely line up. By his third start last year, Wilson was facing Brad Penny and in his fourth, he faced Ervin Santana. Without going start by start, I am not sure the best way to look at matchups like this, but I would be surprised to learn that rotation spot has any measurable impact on a pitcher’s season.

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