Study · Player evaluation
What Carries Over From Triple-A
Strikeout rate travels to the majors almost intact. The batting line does not. And hitters 28 and older get a fraction of the chances, though their numbers translate just as well.
We followed 798 cases of a hitter batting at least 200 times in Triple-A one season and at least 100 times in the majors the next, from 2015 to 2026. The question is which parts of a Triple-A line still describe the hitter a year later against major league pitching.
Strikeout rate carries over best. A hitter's Triple-A strikeout rate correlates at 0.70 with his strikeout rate in the majors the next year, close to the 0.81 we see from one major league season to the next. Walk rate (0.54) and isolated power (0.44) carry over partly. Batting average on balls in play barely does (0.30), and the overall line, wOBA, correlates at just 0.21.
The level of everything drops. The typical hitter struck out 21% more often in the majors, walked 22% less and lost 17% of his isolated power. His wOBA fell from 0.356 to 0.306, keeping 86% of its Triple-A value.
That rate of carryover barely changes with age: hitters kept between 85% and 86% of their Triple-A wOBA in every age group. Opportunity changes a great deal. Of Triple-A hitters 24 and under, 44% batted 100 times in the majors the next season. Of those 28 and older, 7% did.
Pitchers show the same pattern. Triple-A strikeout rate correlates at 0.47 with major league strikeout rate the next season, walk rate at 0.39, and home run rate at only 0.09. Home runs allowed rose 35% on the way up.