Adjusting For Opponent In The 2011 MLB Season

People love baseball statistics. People have always loved baseball statistics, but people might love baseball statistics now more than ever. Maybe because there’s such a broad selection that everybody is free to pick whichever numbers they want. It doesn’t matter if batting average and wins don’t appeal to you anymore. The people who love batting average and wins can stick with batting average and wins, and the people who don’t can opt for anything from wOBA to UZR to OPS+. Mankind loves choices.

As we’ve come to better understand different ways of analyzing the game, we’ve also come to better understand the need to adjust our statistics for a number of different variables. The most obvious is ballpark environment. We know that we can’t just compare someone’s numbers in San Diego to someone’s numbers in Colorado without making some kind of adjustment. Another is overall league context. If offense is up, or if offense is down, then this context must be considered when talking about what a player’s statistics mean.

There are a few of these variables for which we usually remember to adjust. But there’s one that still doesn’t get the attention it deserves, and that’s the quality of one’s opponents. Players and teams don’t face the same opponents over the course of a season. Some will face tougher opponents, and some will face easier opponents, and this will have an effect on the final numbers. But still, few people pay this any mind, which is weird since it’s such an obvious thing to consider.

To be honest, the biggest obstacle might be that opponent quality statistics are almost impossible to find. It’s hard to talk about something if you don’t know where to find the data. Thankfully, Baseball Prospectus exists. There, they present data on which hitters and pitchers have faced the easiest and toughest opposition. And so to give you a taste, I’m going to present four 2011 leader boards.

Hitters who have faced the easiest opposition

Hitters who have faced the toughest opposition

Pitchers who have faced the easiest opposition

Pitchers who have faced the toughest opposition

So there you go. If you’re ever interested in quality of opponent statistics down the road, be sure to check out Baseball Prospectus, because their numbers are updated daily. And don’t forget to take this into consideration when you’re talking about a player’s performance. While most players’ opponents end up roughly averaging out over time, at the extremes it can still make a pretty big difference.