Do Full-Time At-Bats Improve a Hitter’s Performance? by Jeff Zimmerman May 26, 2021 Today, I’m going to take a stab to answer the simple question: “Do hitters perform better with regular at-bats?” While the question is simple, finding an acceptable answer is not so easy. While my final approach is far from “perfect”, it verifies the statement is true to a small extent. The concept behind the rule-of-thumb is that with regular at-bats, a hitter can get into a groove and perform better. Usually, the idea references a hitter in a platoon. Besides being in a platoon, he could be in the National League and used primarily as a pinch hitter. Anyone going from mainly being a pinch hitter to a full-time role will no longer occur the pinch hitter penalty. To find a group of hitters to compare their stats, I took hitters from 2010 to present day jwho: Had between 10 and 50 PA in month #1 that prorates out to 60 PA to 300 PA for a season. They spent no time on the IL or moved to and from the minors in the first month. I wanted the hitter on an MLB club but not playing. Accumulated 90 PA (540 PA for a season) or more in the second month. In all, 192 hitters made the cut. It far from ideal, for the main reason the samples have to perfectly fit into a month’s timeframe. Average & Median Stat Change When Going From Part-Time to Full-Time At-Bats Stat Average Median K% -0.1% 0.7% BB% -0.4% -0.2% BABIP .009 .010 ISO .004 .004 OPS .013 .021 A 20 jump in OPS isn’t going to turn a hitter’s season around. It helps for sure, but hitting full-time is not a game-changer. Again, the measurable differences can likely be explained away by the effects of pinch-hitting. All the gains (BABIP and ISO) are from making better contact that could be from seeing a starter more than just once. To look at it another way, 102 (53%) hitters improved and 90 (47%) got worse with full-time at-bats. It’s really close to being 50/50. On average, going full-time will give a hitter a small boost in their production, but not enough to turn around a hitter. From now on, I’m going to assume a hitter with a full-time role will just keep performing as they always have. Any expected improvement is negligible.