Frayed Knot wrote: ↑Sun Jan 19, 2025 10:36 am Simply the gap between a player's BA & OBA. The difference, unless significantly affected by HBPs which is barely relevant for most hitters, measures how often a hitter draws a walk. 65 to 70 points has been the traditional average and it's not a rate that varies much over time. It was 69 in 2024 for MLB as a whole.
From his ML debut through his CIN & SEA seasons (2017 - 2022) when Winker was more or less a full time player, his BA/OBA gap was 104, significantly above league averages and even his 'down' rate as a Met (75) was still higher than league norms. For comparison, Keith Hernandez was 88 over the length of his career.
You can usually find ultra high rates in power hitters where both careful pitching and high numbers of IWs start to play a major role such as Giambi (122) or Thome (126), or freaks like Bonds (146) and Williams (138)
So this conversation we've been having over calculating a batter's walk rate has been nagging at me all afternoon, ever since we had it. I knew something was wrong and am now angry with myself for not seeing it immediately. Your method doesn't work -- for several reasons. First of all, there's the problem with HBP's, which you recognize and acknowledge. Your method also inflates the walk rate of batters who have many sacrifice hits and sacrifice flies. A sac lowers a players OBP, but doesn't affect a player's BA because a a sac is neither a hit not an AB. Your method thus inflates a batter's walk rate because a SAC lowers a batter's OBP without affecting his BA.
But even if you wanted to concede these flaws on grounds that sacs and HBPs don't happen often enough to have a major influence on your numbers - your math doesn't work.
You can't accurately subtract averages from each other unless the denominators in those averages are equal. The denominators for the same player's PAs and ABs are different because not all PAs are ABs.
I'll illustrate:
A batter goes two for two in his first two at-bats. His BA is 1.000. His OBP is also 1.000. You would subtract his BA (1.000) from his OBP (1.000) to get his walk rate, which in this case is 0. That result is correct. The batter hasn't drawn a walk. Yet. But watch what happens when that batter draws a walk in his third plate appearance.
His BA stays at 1.000 because he got two hits in two at-bats. The walk is neither a hit nor an at-bat, and so has no effect on his BA. His OBP also stays at 1.000 because the walk is a plate appearance and the batter reached base in all three of his plate appearances without making an out. Your method would now produce a walk rate of 0 -- a 1.000 OBP minus a 1.000 BA. And that's wrong. The batter's walk rate is .333, based on one walk in three plate appearances. This doesn't work out.
Now suppose that the batter, in his fourth plate appearance, finally makes an out. His BA drops from 1.000 to .667 (two for three). His OBP drops from 1.000 to .750 (2 hits and a walk in four plate appearances). Your method yields a walk rate of .083 -- (.750 -.667) But the batter's true walk rate is .250 based on one walk in four plate appearances. That's obviously wrong. The size of these errors will surely shrink as the batter accumulates more plate appearances and the numbers you work with get larger. But the math will still be off. Always. Unless the batter never draws a walk.