Everyone knows that pitchers have much more difficulty the third time through the lineup. Right? Isn't this established baseball knowledge?

Data does back it up. Anecdotally we hear stats on almost every baseball broadcast about how much poorer a pitcher performs his third time through the order. League wide there is data to support this claim. According to OPS+ here is how starting pitchers have performed the first, second and third time through the order this season.

PA#1: 91 OPS+

PA#2: 101 OPS+

PA#3: 117 OPS+

Wow! There is a huge difference between a 91 OPS+ batter and a 117 OPS+ batter.

We can see it in the ERA also.

PA#1: 4.08

PA#2: 4.20

PA#3: 4.57

Teams may be making significant decisions based on this data.

I am skeptical. I think the data is very skewed by the group. A pitcher facing a team the third time through is guaranteed to face the better hitters on the team and unlikely to face the weaker hitters on a team the third time through. We can see it in the data.

PAs 1st time through: 37803

PAs 3rd time through: 22470

The majority of those missing 15333 plate appearances come from players who would have been batting at or near the bottom of the order. The top 6 position is the batting order have an OPS+ of 110. The bottom 3 (excluding pitchers) have an OPS+ of 87. I don't have data including pitchers for the group but the 9th place hitters have an OPS+ of 56 with pitchers so that 87 would certainly be lower.

That OPS+ range of 23 between the early part of the order and the bottom of the order nearly matches the OPS+ range of 26 between the first time through the order and the third time through the order.

Maybe this shouldn't be established baseball knowledge. Maybe a pitcher's performance really hasn't dropped significantly the third time through. Maybe it is the statistical illusion created by the group. The majority of the hitters in the third time through group are simply the better hitters.

I wondered if there might be a different angle to attack the question of whether a pitcher's skill level really drops the third time he sees a hitter.

I used baseball reference play index and looked at the group of batters instead. Using the season 2015-2017 and selecting a minimum of 570 plate appearances in those seasons I created a group of 294 batting seasons. I wondered if those batters as a group performed significantly better the third time they saw a pitcher.

Here is the median OPS+ of the group according to time through the order.

PA#1: 101 OPS+

PA#2: 102 OPS+

PA#3: 105.5 OPS+

The third plate appearance was better the third time through. The range as we often hear when reported in terms of pitchers is not nearly as vast. In fact it might not be worthy of comment on a broadcast.

Of the 294 seasons for a batter in 2015-2017, 113 of those seasons the batter had their best OPS in their third at bat.

PA#1 - Best OPS 31% of batters

PA#2 - Best OPS 31% of batters

PA#3 - Best OPS 38% of batters

More batters had their best OPS+ the third time they saw a pitcher. I wouldn't describe it as many more though. I am not sure that a pitcher's ability drops that significantly the third time through the order. I think much of the reported difference is simply the group of batters who they happen to see the third time through.

Batters do seem to perform slightly better the third time they see a pitcher over the last three seasons. Is that difference enough to drive decisions about a pitching staff? Is the opener a solution to this problem? Does a real problem exist? Those better hitters at the top of the order are likely to get an extra at bat against someone every game. If the solution is using an opener, that opener is going to have to be a really good pitcher to get through a team's best hitters.

Note: Baseball Reference Play Index was used to gather the data.