Walk-offs Above Replacement: How we think about value

By virtually all metrics, Aaron Judge is the frontrunner for the American League MVP as we approach the halfway mark of the season. He’s the best player on the best team, in the top five in pretty much every offensive stat, and of course is making a real run at 60 home runs. He also has three walk-off hits, game-ending moments that help drive a narrative that this guy is the one you want at the plate, above all others, when you really need a big hit.

The fact that two of those game-winning hits came against the Astros, the likely biggest rival for the AL pennant, only goes to further that narrative, and got me thinking about narratives as a whole. What’s the intrinsic value to a walk-off? A run-scoring single is just that, worth about .89 runs according to wOBA, the basis of fWAR. Since that metric doesn’t really care about context, a hitter gets the same credit for a single in the third inning with nobody on as they do in the ninth with the bases loaded.

Stats that do incorporate, or at least attempt to incorporate context, have their warts too. WPA exists in a binary system where only the pitcher and hitter can receive credit or blame, and batting average with RISP is too volatile year-to-year to be relied on. Lastly, there’s the opportunistic nature of a walk-off itself — a player needs to be given the chance to end the game themselves, but has little to no control if they’ll come up to hit in the critical spot.

Still, how valuable is one walk-off hit? Two walk-off hits? Five? Everyone already knows Aaron Judge is one of the very best players in baseball, but what about the average player who just happens to come through a few times a season?

We are fortunate enough to have the model example available to us, 2009 Andre Ethier, who set the modern record for walk-off hits in a campaign, with six. He had a perfectly good 2009, with a 129 wRC+ and a dreadful defensive output that led to about a two and a half win season, not dissimilar from Miguel Andújar’s 2018 — a fine season, no question, but not MVP caliber.

Some combination of his 105 RBI and six walk-off hits, though, clearly built a narrative around Ethier’s value, that this guy was the guy you wanted at the plate in a big spot. He finished sixth in NL MVP voting that year, ahead of an eight-win season from Chase Utley and six-win seasons from Adrian Gonzalez and Ryan Braun.

I don’t know if that would happen again, but what would the value of a nine, or ten, or eleven walk-off player be? You’re banking ten wins for the team, ten wins that by definition would have come in close, tight, high-leverage games. That value may not be borne out in WAR, but it would probably be impossible to ignore from an evaluation standpoint.

Ten walk-offs would almost guarantee you a slot at the top of the WPA leaderboard, a metric that does attempt to apply context to the “value” of your hits. Right now, the top five players in WPA are Mike Trout, Judge, Manny Machado, Rafael Devers and Yordan Alvarez, which shouldn’t really surprise anyone who’s followed the game this year. One of the ways to adjudicate metrics is to ask whether a leaderboard visually make sense — we know who the best players in baseball are, they should be all over the top of a given stat.

In 2009, Ethier had the fifth-highest WPA in the game, despite being the 36th-best hitter. If Josh Donaldson, who’s been better than average but not really anything to write home about, made a run at Andre’s walk-off record, and was that high up the WPA ranking, would we consider him an MVP candidate? I’m not sure.

Aaron Judge is having a magical season, nearly halfway to the AL HR record and halfway to the walk-off hits record. I think the former means a lot more to a player’s overall value than the latter, but there’s something about a player ending the game on his own terms that just makes you shake your head. It might exist outside the conventional means of determining value, but its part of why we love the game.