You've seen the Win Probability graphs in our recaps, that tally the ebb and flow of a game over its course. The numbers used for this can also be used on an individual basis to figure out how much impact a player has had on a game. WP was 50% before his at-bat, and 60% after? Give him 10% credit. Add that up over the season, and you get a number that reflects performance, weighted more heavily to how they did in "high leverage" situation i.e. with the game on the line. Down by one in the ninth, with a man on second, will be seen as more important - positive or negative - than up by six in the fifth inning.
It's not a perfect measure, because there are gaps - if a hitter reaches base as the result of an error, for example, they get credit for it, even though it wasn't really their responsibility. Indeed, there's no component in this for a player's defense at all, be that good or bad. Before even pulling up the figures, I will therefore predict that Nick Ahmed is going to be unfairly jobbed by this metric, and Yasmany Tomas will look better than he "really" is. But it still offers an interesting snapshot of how the members of the team have performed. I've broken it down into hitters (min 20 PA - sorry Phil Gosselin, Chris Herrman and Rickie Weeks Jr), starting pitchers and relievers.
Yeah, seems lefit. By more traditional fWAR, Jean Segura has already been worth 0.7 bWAR in 11 games (he was worth a total of 0.2 in 2013 and 2014 combined!). What really stands out for me is Segura's K-rare is way down: it was 15.9% last season, but so far has only been 6.7%. He's also walking a bit more, though that remains an area of possible improvement. Behind him come Paul Goldschmidt and Ahmed - almost level on WP, but Nick has the clear edge in fWAR, and is second on the team at 0.4. At the other end? Chris Owings. Ouch. Still waiting for his first walk, and not coming through in a push either, through Brandon Drury is actually slightly lower by fWAR (-0.3)
In fWAR terms, there hasn't been much to choose between our rotation, with all of them save Shelby Miller coming in at 0.1 or 0.0 - Miller is -0.3. But WP does differentiate them more significantly. Robbie Ray has clearly been the "best" - that's because, while his overall numbers have been similar to Patrick Corbin, Ray's performances have come in "more important" situations. His average "leverage index", which measures that importance, is 1.21, compared to Corbin's 0.82, the lowest among the five starters. Greinke was helped by last night, his first positive outing, but overall, Arizona's figure of -151% ranks last in the majors, 15 points below the next-worst.
This passes the smell test, as we see the gulf between the A-bullpen and the rest. Brad Ziegler, Daniel Hudson and Tyler Clippard have been worth.+93%; everyone else has combined for -97%. Mind you, we were likely a bloop single last night from a rather different picture, though Z doesn't get credit for escaping that jam, since it was of his own making. But it does show how volatile things can be, especially at this point of the season. If the Padres had won last night's game in the ninth inning, Ziegler would have been awarded -82.7%, rather than +17.3%, and would as a result be our worst reliever. Instead, that's Randall Delgado, mostly due to Thursday's meltdown.
I'll revisit these every couple of weeks, to see how things change over the course of the campaign, and how this compares against other measures of our players' worth.