MLB on Record Pace for Extra-Inning Games in 2013

Last Saturday the Marlins and Mets played 20 innings and the Blue Jays and Rangers played 18. I found myself wondering how often two games on the same day had each gone so many innings. I began researching and was fairly quickly able to find an answer to that question*, but (as is often the case for me) then I found myself wondering about other extra-inning game tidbits. Suddenly I was immersed in hours and hours of research. One thing I discovered while working my way through the mountain of data I wanted to go through: 2013 is on pace to have more extra-inning games than any season in MLB history.

*Since 1916, (as far back as I can go using Baseball-Reference's wonderful Play Index database), only once before had two games on the same day gone 18+ innings. That was August 15, 2006, when the Diamondbacks and Rockies and the Cubs and Astros each played exactly 18 frames.

As of this morning (Friday, June 14), there have been 110 extra-inning games around baseball so far this season, out of 983 total games played (out of 2,430 scheduled to be played over the entire season). That means MLB is on pace for 272 extra-inning games.

Seasons with the highest number of extra-inning games*:

2011: 237

1986: 220

1991: 220

2007: 220

2010: 220

*As I said above, the Play Index for this sort of thing dates to 1916, so all figures you see are from then on.

As you can see, 2013 isn't just on pace to break the record, it's on pace to shatter it. Regression to the mean tells us that anyone or anything on a record pace is likely to see their pace fall off. 2013 is far enough ahead of pace though, even as the pace slows, it's still got a very good shot at breaking the record.

In addition to the two marathon games from last Saturday that I already mentioned, there have also been  two other games in 2013 that went 18+ innings (including the A's/Yankees contest just yesterday). That seems like a lot of extensively-long games for such a short timeframe, three such games in under a week and four of them in under two months.

Seasons with the highest number of 18-inning (or longer) games:

1967: 9

1972: 6

1918: 5

2013 is on pace for a record 10 such games and is already in a tie for the fourth-most marathon games (1969, 1971, 1973, 1984, 1985, and 2006 also had 4 games last 18+ innings).

A record pace for both extra-inning games and especially long games seems like a recipe for also playing the highest number of total extra innings (a 10-inning game being 1 extra inning, an 11-inning game being 2 extra innings, etc.)

Seasons with the highest number of total extra innings:

1980: 531

1976: 519

1982: 518

1992: 515

2011: 504

In 2013 there have been 245 total extra innings thus far, putting the season on pace for 606, far beyond the current record. Regression to the mean will almost certainly bring that number down, but perhaps not so much that we still don't get more extra innings than in any previous season.

The extra-inning games in 2013 haven't actually been particularly long though, despite their having already been 4 games that went 18+ innings. If you divide the 245 total extra innings thus far by the 110 extra-inning games that have taken place, you get an average of 2.227 extra innings per extra-inning game in 2013.

Seasons with the highest average number of extra innings in extra-inning games:

1967: 2.698

1918: 2.593

1972: 2.586

1919: 2.573

1976: 2.569

2013 ranks only 43rd out of the 98 seasons, meaning that despite those 4 marathon games, the average extra-inning game this season has had a fairly normal number of extra innings.

How do you get a 'normal' number of extra innings per extra-inning game when you've got a (relatively) high number of marathons in there? By having a ton of games go exactly 10 innings (the shortest possible extra-inning game, of course). 64 of the 110 extra-inning games so far in 2013 have gone exactly 10 innings. That works out to 58.2%. The highest figure for any previous season is 56.7%, from 1930. So, you have more super-long games than usual, but also more 10-inning games.

There's been a relative shortage of games lasting 11 to 13 innings. Just 32 so far in 2013, putting the season on pace for 79. The last time there were fewer games of 11 to 13 innings than that (not including strike-shortened season was way back in 1968, when there were still only 20 teams.

And THAT brings me to the final thing to be pointed out, something I'm sure some of you have been thinking to yourself since I first mentioned that 2013 was on pace to have a record number of extra-inning games: There are 30 teams now and they each play a 162-game schedule. Until 1961 there were only 16 teams (and they played a shorter schedule too). It wasn't until 1998 that MLB reached it's current size, so it's to be expected that more recent seasons would have a higher number of extra-inning games. What if we look at the percentage of total games that are going extra innings, does 2013 still stand out?

Seasons in which the highest percentage of games went extra innings:

1943: 13.37%

1957: 13.09%

1918: 11.73%

1942: 11.60%

1916: 11.57%

So far in 2013, 11.19% of all games have gone to extra innings, which would rank 6th out of the 98 seasons here. It's not quite a record rate, but it is the highest in 56 years. The next-highest figure from the 2000s is all the way down at 34th on the list (2011, 9.76%) and other year from the 2000s places anywhere in the top half of the rankings.

Summary:

Extra-inning games so far in 2013: 110

Full-season pace: 272

MLB record: 237 (2011)

Total extra innings so far in 2013: 245

Full-season pace: 606

MLB record: 531 (1980)

Number of extra innings per extra-inning game so far in 2013: 2.227

MLB record: 2.698 (1967)

Percentage of total games that have gone to extra innings so far in 2013: 11.19%

MLB record: 13.37% (1943)

One way of looking at this is to say that in 2013 we're on pace to get more baseball than we've ever gotten before, which is just about the best news I can think of.