A few guys have mentioned that there are a lot more R symbols out there this season. Commish & I were talking about it and speculated about how the symbols are calculated. I guessed that the R & H symbols depend solely on how many home runs a pitcher gave up with runners on base relative to the total number of homers he surrendered.

I collected some stats from Baseball Reference to see how they compared to the symbols. I initially selected the 43 starters currently on the ABL active rosters. I later added some H-symbol starters from Taxi Teams and the free-agent pool, because the H symbols were underrepresented. I didn’t look at any relievers, but I don’t expect they would have rules different from the starters. I looked at the 2013 MLB stats and the TPB cards we’re using for the 2014 ABL season. In B-R you can find the relevant stats under the “Splits” menu in the “Standard Pitching” section on the particular pitcher’s page. Scroll down to the “Bases Occupied” table. Strasburg’s stats are shown below: 7 homers with the bases empty, 9 with runners on.

I noticed some patterns and figured out an easy rule that predicted all the actual symbols. It’s best understood by looking at the grid shown below. There are two measurements that figure in. The first is the number of homers hit with runners on base divided by the total number of homers. Call this HR_{onbase}. My initial thought was that the symbols would depend on this number only. The average value of this measurement in my sample is 40%. The second measurement is the overall home-run rate: the total number of homers surrendered divided by the batters faced. Call this one HR_{t}. The average value in my sample is 2.2%. So here’s the table showing how the combination of these measurements determines the symbol:

When the overall home-run rate is greater than 2%, the symbols act like I expected them to. If the percentage of home runs with runners on is large, the guy gets an H. If that percentage is small, he gets an R. But it’s a different story when the overall home-run rate is less than 2%. In that case, it doesn’t matter what the stats are for on-base and bases empty; the guy gets an R, period. The clearest example is Henderson Alvarez, who had guys on base __every time__ a home run was hit against him. But that was only two homers in 418 plate appearances, a very low rate of 0.48%. That low rate earned him an R, despite the fact that he gave up zero solo shots.

So it’s obvious that the R symbol is used to reduce the number of homers from the batter’s card when the pitcher gives up fewer than average home runs in general. With power becoming scarcer recently, it’s not surprising that more Rs are required. On the other hand, although there were 273 fewer home runs in 2013 compared to 2012 (as Commish pointed out), there were even fewer in 2011.

I wondered why the overall homer rate couldn’t instead be handled via the Deep ranges. I think the answer is that if you lose the Deeps, then you lose the park variation that forms such an important part of the game. If a guy has no Deep ranges (and there are some, of course), then it doesn’t matter what park he’s pitching in or what Power the batter has (except for the Deeps from Park Effects, of course).

So, my conclusion is that the R & H symbols are based more on the overall home-run rate of the pitcher, and not so much on the state of the bases when the home runs were hit.