During a season, I often get an impression about the Rangers that may or may not be true. For example, a few weeks ago, I felt like Ranger pitchers were walking the #9 hitter at a high rate. So, I asked Jared Sandler on Twitter, who is very good with Ranger stats, if this was the case. He said that this had occurred to him, but when he ran the numbers they were walking the #9 hitter at about the same rate as the rest of the league. Many times, my impressions are worse than reality.
Last night the Rangers faced Oakland’s Sean Manaea for the second time this season. When the Rangers faced him the first time, he came into the game with an ERA of 11.37. The Rangers managed 1 earned run in 6 2/3 innings. Last night, Manaea came into the game with a 6.02 ERA, and the Rangers could only manage 2 earned runs, in what became a 14-5 loss. Over the last few seasons, I’ve gotten the feeling that the Rangers tend to perform poorly against pitchers who come into the game with a high ERA. I don’t know why this would be the case. One of my theories is that the Rangers hitters have a hard time hitting pitchers who throw with a lower velocity. For example, the knuckle-baller R.A. Dickey has a 0.63 ERA against the Rangers this season. In 14 and a 1/3 innings pitched, the Rangers have managed only 1 run against Dickey and are hitting a horrible .180. Overall he has a 4.16 ERA. The best ERA he has against any other team is a 2.57 against the Dodgers (over one start).
So, my gut feeling here could be correct, or it could be based on what I remember from the Rangers facing Manaea and Dickey. I decided to take a look.
I went through the Rangers’ schedule and compiled a list of every starting pitcher they have faced this season. I added to the list each pitcher’s ERA going into the game, whether the Rangers won or lost, the score, and how many earned runs the Rangers scored on that starting pitcher. I then sorted the data based on ERA and divided it between pitchers who went into the game with an ERA below 4.00 and those who went into the game with an ERA above 4.00.
Against pitchers with an ERA below 4.00, the Rangers averaged 3 ER. Against pitchers with an ERA above 4.00, the Rangers averaged 3.13 ER. Not much difference there.
I then looked at total runs per game. Against a team who started a pitcher with an ERA below 4.00, the Rangers averaged 4.74 runs per game. Against a team who started a pitcher with an ERA above 4.00, the Rangers averaged 4.8 runs per game. Again, not much of a difference, but in both cases the Rangers did slightly better against pitchers with a higher ERA. Statistically, this makes sense, but it does not support my impression that the Rangers struggle against bad pitchers. On the contrary, they seem to perform about the same, regardless the ERA of the starting pitcher.
Finally, I looked at wins and losses. This is where the data gets a little interesting, particularly since the Rangers seem to score about the same whether or not a starter has a high or low ERA. The Rangers’ record when their opponent starts a pitcher with an ERA below 4.00 is 14-13, for a win percentage of .518. So, essentially 50/50. That makes sense and shouldn’t be a surprise. When the opponent starts a decent pitcher, the Rangers win about as often as they lose. When the opponent starts a pitcher who has an ERA above 4.00 the Rangers’ record is 22-8, for a win percentage of .733. This is a huge difference, especially since the Rangers do not seem to score any more runs against teams who start a pitcher with an ERA above 4.00. It shouldn’t be a surprise that the Rangers win at a much better rate when the opposing pitcher has a high ERA. But, it is surprising that they score about the same amount of runs against pitchers, regardless of ERA, but clearly tend to win more when the opponent starts a pitcher with a higher ERA. So, what gives?
I looked at how many runs the opponent scored in games where they started a pitcher with below a 4.00 ERA and above a 4.00 ERA. When a Ranger opponent started a pitcher with an ERA below a 4.00, they scored an average of 4.85 runs per game. When a Ranger opponent started a pitcher with an ERA above a 4.00, they scored an average of 3.7 runs per game. A sizeable difference, especially compared to the Rangers average runs per game of 4.8, in the same scenario. That’s almost an entire run per game more, and at least in part, explains why the Rangers win more games against pitchers with higher ERAs even though they aren’t necessarily scoring more runs. Their opponents’ struggling pitchers are getting less run support. That can’t be encouraging.
In the end, another one of my assumptions seems to be incorrect. The Rangers aren’t doing any worse against pitchers with high ERAs. In fact, they tend to do about the same, regardless of whether the starter comes in with an ERA above 4.00 or below. They do win a whole lot more games against struggling starters, but that has much more to do with the run support those starters are getting than the Rangers’ ability to score runs against them.
*I excluded pitchers who had their first start against the Rangers, since each would naturally come into the game with an ERA of 0.00.