August 4, 2011
Why When You Go Matters
We’ve heard the argument against RBIs a million times. It begins with name-calling and ends with being called names, but in between, the rational party explains that Runs Batted In do not control for context. Batters do not get to choose when they hit with runners on base. The same logic can be applied to win probability added—a measure that assigns credit based on the shift in a team’s win expectancy over the course of play.
A walk-off grand slam in a tie game might be worth 4 RBI and raise the team’s win expectancy to 100%, but the batter does not deserve more credit for that home run than for most other home runs. In fact, a single would have been just as good. Batters can alter their situational hitting but not their hitting situations. The accepted solution* has been linear weights, which gives batters credit for their contributions devoid of any context. An average home run is worth 1.4 RBI or 0.14 WPA.
*I believe the answer lies in WPA/LI, but that’s another argument for another day with another round of name-calling.
Baserunning is a different story. There is little reason to assign a blanket value to stolen bases other than for simplicity’s sake. A stolen base attempt is entirely dependent on the game state and under the baserunner’s control. Thanks to Retrosheet and Baseball Prospectus’ historically-based year-by-year win expectancy tables, I was able to assign each stolen base, defensive indifference, and caught stealing since 1954 a win probability added figure. Here are the top ten basestealers of all-time, by WPA:
The crux of all baserunning analysis hinges on breakeven rates. Most stolen bases increase a team’s chance of winning by two percent, and caught stealings result in a four percent loss. Therefore, batters need to be successful twice as often as they are caught to break even—a 67% breakeven rate. Those numbers fluctuate depending on the game situation. As the breakeven rate goes up, basestealers become choosier. Nonetheless, given the extreme lack of caution in the 1950s and 1960s, the zero-sum game has historically tilted in the pitching team’s favor.
Keeping breakeven rates in mind, the best basestealer is not merely the one who has the highest success rate. Oftentimes, baserunners should expect to be thrown out; think of the third-base coach waving a runner home with two outs and a .250 hitter on deck. The best basestealer has a high success rate, while also taking advantage of his ability by running as often as he possibly can whenever his expected success rate is marginally above the breakeven rate.
Rickey Henderson was the greatest basestealer of all-time, but his stolen-base percentage does not stand out. Arguably the second-greatest basestealer ever, Tim Raines, was renowned for his success rate. Let’s take a look at what separated Henderson from Raines.
Both Raines and Henderson added value by stealing bases so long as the breakeven rate was below 90%, and that’s what really matters. Raines adding more value for every marginal steal is outweighed by his being so picky when the breakeven rate was down near 70%.
Carlos Beltran has been a fantastically gifted runner, but he’s lacked aggression on the basepaths. His success rate was consistently above 80%, regardless of the breakeven rate, and he did not attempt to steal much more often in more advantageous situations, in contrast to the rather mediocre basestealer Juan Pierre.
I also checked out the two most controversial players ever, one a top-50 basestealer and the other the worst basestealer.
I’ll close with a word on Brett Gardner. Coming into the year, Gardner was the only player with at least 100 stolen base attempts to have averaged 1% WPA for each attempt. He was at 1.3%. That alone puts him among the top 50 basestealers of all-time, but it does not mean that he is one of the 50 smartest. In all likelihood, he should have been getting caught more often, as anyone racking up a 90% success rate is not taking enough risks. Even if he was the best basestealer in the game, he could have been better.
Gardner started off 2011 by being caught a bunch of times. Oddly, the frustration over his being too conservative instantly morphed into frustration over his not being a good basestealer at all. This did not make sense. The best basestealers should be the ones getting thrown out the most often, and the worst should be the ones who never run.
Here’s the complete table.
The data: I looked at situations with a man on first, a man on second, men on first and second, or men on first and third. A stolen base of third with men on first and second assumed that the trail runner took second and gave the lead runner the entire WPA for that event. A stolen base attempt of second with men on the corners assumed the runner on third remained on third. The swing is the leverage of the stolen base attempt. In a situation in which a CS is -15% and a SB is 5%, the breakeven rate is 75% and the Swing is 20%. Retrosheet does not contain full pitch-by-pitch data for all games, so many were excluded in calculating attempt rate. I included only situations in which the runner by the end of the at-bat had had an opportunity to steal on a called ball, a pitchout, a called strike, or a swinging strike.