Overlooked MLB Stats: xERA vs Actual ERA & Pitching Luck vs Fluke Wins

It’s no secret that pitching drives MLB betting because no player on the field has more control over the game than the pitcher. The problem is that the best pitcher with the best stats isn’t the one who always wins the game. Being able to spot when a starter is going to come out and throw as his record indicates is something a lot of people struggle with. That is why I want to take some time to explain two different methods of determining how a starting pitcher will perform on a given start.

Expected ERA (xERA) vs. Actual ERA

xERA is a statistical formula that was created by Dwight Gill and Tad Reeve that gives you a gauge of how well a pitcher is performing compared to his actual ERA. The actual ERA is the stat that tells you how many earned runs a pitcher allows on average for every nine innings of work. While a pitcher’s actual ERA gives you a pretty good idea of how well a pitcher is performing, we feel it leaves out some key aspects of the game.

xERA is calcuated by taking  ( (.575 x H/9 ) + (.94 x HR/9 ) + (.28 x BB/9 ) – (.01 x K/9 ) – Normalizing Factor). The Normalizing Factor is based on the league during a given year and is typically around the .270 to .285 range.

By taking a little extra time to see if a pitcher’s actual ERA is close to his xERA you can get a much better feel for how that pitcher is going to perform in his upcoming starts. If a pitcher has a low actual ERA and a high xERA, his ERA is misleading and chances are he is going to come back to reality sooner than later. On the other hand, if you have a pitcher with a high ERA and low xERA, odds are that pitcher is going to start to see some better results down the road.

Pitching Luck with Fluke Wins

Baseball is believed to be the one sport where luck can really play a factor in how well a particular player appears to be performing. A pitcher can take the mound and miss his spot time after time but still manage to get hitters out by having them hit line drives right at the defense. There is also the case where a pitcher can make an amazing pitch, but still manage to give up a hit on a broken bat single or slow roller up the line.

While luck can be on a pitcher’s side on a given string of starts, odds are the luck is going to change over the course of the season. This is why it is important to look past the overall record of a given starter and take the time to see how well they have actually been performing.

For example, say you have a starter on a given team that is 2-5 with a 3.23 ERA in 10 starts, while another starter on that same team is 5-1 with a 4.65 ERA in the same amount of starts. There are a number of different things that could factor into why the starter with the 4.65 ERA has ended up with a better record up to this point;  run support, defense, bullpen, location of the game, etc.

What you need to understand is that because baseball is played over a 162-game season, more times than not a pitcher’s record is going to end up resembling his performance on the mound. The starter with the 5-1 record and 4.65 ERA is more likely to not have things go his way in his next start, while the starter with the 2-5 record and 3.23 ERA is more likely to come out with a win in his next outing.

I understand that this may seem a bit simple for someone who has been watching baseball for a long time, but I routinely see this mistake being made over the course of the season.  The betting public will continue to back the pitcher with a strong record and high ERA while staying away from pitchers who have a bad record and low ERA.

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