The Myth Of The Modern Jet Stream

Is Globe Life The Ballpark in Arlington no longer a haven for offense?

If you tune in to ESPN or MLB Network for Rangers' highlights, the idea would be ridiculous. The phenomenon known as the jet stream is still as synonymous to TBiA as batting average, RBI and HRs are to baseball itself. Or, at least baseball the way those people see it. I've always more or less thought of the jet stream as a copout by whichever network was carrying the game. It's almost a way of saying "It wasn't our pitcher's fault, it was the jet stream's fault."

This may be because the only Rangers' games I got to see as a kid were when they played the Angels (my local team) on Fox Sports West. Whenever an Angel hit a home run, Steve Physioc and Rex Hudler would say how the Halo hitter crushed the ball, but whenever an Anaheim pitcher gave up a home run it was because the Rangers' hitter "found the jet stream." It might be subtle, but it's homerism at its finest. 

Plus, it's convenient for the narrative. And since it's comfortable and universally accepted there's no real need for anyone to stop perpetuating the idea of the jet stream.

But I'm not so convinced anymore. 

After the 2012 season, Richard Durrett of ESPN Dallas wrote an article about the removal of a section of the stadium behind home plate, even noting that it "... [leaves] an open area for fans to not only see the field, but for the wind to blow through as well".

Now, I'm not a wind doctor. But there is data to suggest, contrary to popular opinion, Texas's home park may have turned into a neutral offensive park. 

Starting last year -- the first full season after the ballpark modifications -- the Rangers' have both (a) pitched better at home than on the road, and (b) hit virtually the same home and away. In 2013 Texas generated a composite triple slash line of .268/.333/.412 (95 wRC+) at home, and .257/.314/.412 (99 wRC+) on the road;

In 2014, the brief trend has continued: The Rangers have hit just .248/.317/.364 (76 wRC+) at home, and .268/.335/.386 (100 wRC+) on the road. It would be easy to say, "Well, the Rangers just haven't been that good of an offensive team the last two years, so these numbers don't mean a whole lot." And to that I would agree; and, sure, 1.25 years is still a relatively small sample. But if we take Texas's offense out of the equation, then what?

The Rangers' pitching staff hasn't been very good in 2014. They are 12th in the American League in ERA (4.45), 12th in xFIP (4.15), and just 12th in strikeout rate (19.1%). Their saving grace has been a solid groundball rate (44.3%, 6th in the AL), and the ability to limit the opponent from going yard (8.8% HR/FB, 5th in the AL). If not for some batted-ball fortune, the pitching staff would look even more helpless than it already does.

But at Globe Life Park -- supposed jet stream and all -- the staff ERA is 4.24, half a run less than on the road (4.73). If we look at 2013, the Rangers finished the season with a 3.45 ERA at home and 3.81 ERA on the road, a marginal but still meaningful difference.

Now, let's look at what the numbers were like before the modifications:



Home: .285/.347/.473 (111 wRC+)

Away: .261/.320/.420 (101 wRC+)


Home: .296/.353/.508 (122 wRC+)

Away: .269/.326/.413 (102 wRC+)



Home: 4.17 ERA

Away: 3.86 ERA


Home: 4.37 ERA

Away: 3.19 ERA


Two years prior to the modifications, the Rangers hit drastically better in Arlington than they did on the road, and the pitching staff was markedly more effective away from home. In the two years since -- 2013 and so far in '14 -- the script has flipped completely. At the Globe, the pitching has been better and the offense has been worse. 

Now, I know ERA isn't the best indicator to judge pitcher performance. I know last year, and some 25 games in 2014, isn't a large enough sample to state definitively whether or not TBiA is still a hitter's park. But there is data to suggest it.

I don't know what that means, if it adds/subtracts from the club's home field advantage. But next time you hear an analyst or commentator blame a pitcher's fortunes from the jet stream, just know it wasn't that. The hitter has to earn it nowadays.