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Strikeout-to-walk ratios hitting record levels

Baseball by the Numbers: The Sox’ Carlos Rodon and the Cubs’ Adbert Alzolay are part of a growing trend.

Sox left-hander Carlos Rodon has struck out 5.17 batters for every walk he has allowed this season.
Sox left-hander Carlos Rodon has struck out 5.17 batters for every walk he has allowed this season.
Frank Franklin II/AP

As strikeouts continue to soar in baseball, so do strikeout-to-walk ratios. White Sox left-hander Carlos Rodon and Cubs right-hander Adbert Alzolay have joined the trend.

In the American League-National League era starting in 1901, the top 11 seasons for K/BB ratio are the last 11. The 2019 season leads the parade with 2.69 strikeouts per walk. The ratio is a tad higher in 2021 — 2.70 — through Sunday.

With 62 strikeouts and 12 walks, including 13 strikeouts and no walks in six innings Friday against the Yankees, Rodon’s ratio stands at 5.17. Alzolay, who struck out six and walked none in seven innings Saturday against the Cardinals, has an even better ratio at 6.43 (45 strikeouts, seven walks).

Neither has quite enough innings to be listed among the leaders, but if innings are set at 42, Alzolay ranks eighth and Rodon 16th in the majors.

Gerrit Cole (11.50), Zach Eflin (11.40) and Julio Urias (10.00) are on paces that would break Curt Schilling’s modern-era (1901 and later) record of 9.58 in 2002.

At his pace, Rodon would rank high in Sox history. Among Sox pitchers with enough innings to qualify for the ERA title, only Chris Sale has exceeded five strikeouts per walk three times. Sale set a club record at 6.52 strikeouts per walk in 2015 and was at 5.33 in 2014 and 5.18 in 2016.

The Cubs’ record is held by Hall of Famer Ferguson Jenkins, who struck out 7.11 per walk in 1971 (263 strikeouts, 37 walks).

Jenkins had exceptional walk rates throughout his career, but the current trend is driven by the strikeout explosion, not by a reduction in walks.

In 2010, pitchers struck out 7.1 batters per nine innings. The strikeout rate has increased every season since, reaching 8.9 in 2020 and 9.1 so far in 2021.

Walks stood at 3.3 per nine innings in 2010, were at 3.5 in 2020 and are at 3.4 in 2021. They declined to 2.9 in 2014 and 2015 but have recovered since.

The result is that there are more walks now than there were in 2010, but the K/BB ratio that hit a record 2.17 in 2010 has mushroomed to the 2.69 and 2.70 of 2020-21 because there are so many more strikeouts.

The walk rate has waxed and waned within a narrow range for nearly 90 years. Except for 2014-15, it has been at 3.0 or higher every season since 1923 and reached four only twice, with 4.1 in 1949 and 1950.

But strikeouts climb higher and higher, confounding fans who want to see balls in play and baserunning. Turning around the trend will require teams to see benefit in giving roster space to contact hitters. That could require rules changes under consideration, such as moving the mound back, lowering the mound and restricting defensive shifts.

For now, rising K/BB ratios are part of the game, with Alzolay and Rodon ahead of the curve.