The true ‘year of the pitcher’ was noteworthy for a spike in the strikeout rate, and typically assumed to have been caused by some combination of the mound, the umpires and the pitchers themselves. Is that the case here? We do see a statistically observable increase in the strikeout rate, from 17.96% to 18.5%, and a decrease in the walk rate from 8.88% to 8.5% – together these raised the MLB average K/BB ratio from 2.02 to 2.17. Strikeouts and walks are the big things that most everyone can agree that pitchers control, so a noticeable increase in K/BB definitely seems to lay credit at the feet of the pitchers (or umpires). And to the extent that some of our long-term decline in scoring is due to an emphasis on development of young pitchers (and a great crop of young ones now) this could definitely continue. However, this can’t be the only cause… for one thing, both the rise in the strikeout rate and the drop in the walk rate are much more pronounced in the National League – where the drop in scoring was small. It’s true that interleague play exists, but there are hardly enough interleague games to explain the discrepancy.
Since we’re looking for something that changed on pitching staffs across the league, perhaps we should be looking at new players entering the league. Can part of the apparent improvement in pitching be due to an unusually strong crop of rookie hurlers? As it turns out, maybe a part of it can – but looking there suggests something even more interesting. Rookie pitchers in 2010 did have a lower ERA than 2009 rookies, dropping from 4.61 to 4.36. ERAs across the sport dropped from 4.31 to 4.07, so the drop in rookie ERA is almost exactly the same as the drop in ERA among non-rookie pitchers. What does stick out, however, is that rookie pitchers threw a lot fewer innings in 2010 than in 2009. The percentage of total innings pitched by rookies dropped from 22.6% in 2009 to 15% in 2010. Since rookies are worse, on average, than veterans more innings pitched by rookies should mean, on average, lower quality pitching. In addition, if fewer rookies are thrown into the fire we are more likely to be pulling those rookies from the high-end of the talent distribution – so the average rookie should be better. This seems to have the potential to explain the majority of the drop in ERA. While ERAs among veteran pitchers did decline (from 4.22 to 4.02) if rookie pitchers had continue to pitch as many innings as they had in 2009, with the same 4.61 ERA, league ERA in total would have dropped from 4.31 to 4.15 instead of all the way to 4.07.
Of course, maybe we’re barking up the wrong tree entirely by looking for an explanation for the ‘year of the pitcher’ on the run-prevention side. Maybe pitchers are looking good, rookie and veteran, in large part because of limp bats. Check back later this afternoon for the second part of the post, where I break down what went wrong with league offensive production from the hitters’ perspective.