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The Diamondbacks 2014 in Win Probability

If you've read any of our game recaps, you'll have seen the Win Probability graphs, which chart the ebb and flow of the contest over its duration. But which Arizona players were the WP MVPs? And which were

Rob Foldy
Win Probability: what is it?

A quick overview is probably wise. The history of baseball, covering hundreds of thousands of games, tells us what the chances are of you winning the match, in any given situation. Bottom of the seventh. home team down by one, no outs, man on first? History tells us that 43.1% of home teams will win from there. If the runner is on second, your Win Probability goes up to 48.7%, and if he's on third, you've a better than even chance, at 54.5%. Plot the course of this figure after every plate-appearance, stolen-base, etc. and you get a graph. Here's the one for perhaps the year's most exciting game: the June 24 win where we beat Cleveland 10-9 in 14 innings.


On an individual level, this can be used for players as well. Pitcher X faces Hitter Y, with the WP at 60% in favor of the pitching team. Hitter makes an out, and the WP goes to 65% as a result. Pitcher X gets credit of +5% and Hitter Y gets -5% for it. Again, add those up over the course of a game, and it's how we work out the Heroes and Villains for each contest - and add those per-game tallies together as well, to get a sense of which players were most responsible for wins and losses over a season. It's a combination of performance and "clutchiness", because a single in the ninth inning of a tied game is a bigger change in WP, than the third inning of a blowout.

It's not a perfect measure. For instance, hitters still get credit for the results of an error, because WP doesn't care about how the run comes home, just that it did. And it over-values game state, to the extent that you can hit a grand-slam and WP might barely twitch, just because your team is already up by eight runs at the time. But WP is a "skill," in the sense that players with high or low WP one season, tend to have the same the next. Not as much as OPS, but more so than batting average. So, who were the heroes and villains of the 2014 Diamondbacks season?

And the 2014 Paul Goldschmidt Award for Hitter WP goes to...

Paul Goldschmidt. There's a shocker. The award is so named because of his monstrous 2013, where he piled up +786% of Win Probability - more than three hundred percent more than anyone else in Diamondbacks history. This year was a pale shadow, at only +241%. But it was still twice as much as the next person, A.J. Pollock at +112%. No great surprise there. But what might be startling was third-place: Tony Campana? At +81%, that's a function of his use as a late-inning pinch-runner, and the large WP harvested when, for example, he stole second to move the tying run into scoring position.

The 2014 anti-Goldschmidt belonged to... Martin Prado, at -175%, but it was a tough fight, with 20 of the 27 position players we used this year, ending the season in negative WP territory. Prado just edged Mark Trumbo's -165%. That was in no small part thanks to the real rally-killers which were Martin's 17 double-plays, leading the team, even though Prado only appeared in 106 games. So much for "Good things happen when you put the ball in play" - a line I hope our new assistant hitting coach drops from his philosophy. Alfredo Marte (-130%) and Aaron Hill (-114%) were also severely negative - as, perhaps surprisingly, was Chris Owings, at -91%.

And the 2014 Randy Johnson Award for Pitching WP goes to...

Evan Marshall. Yep. Bet you didn't see that one coming. While Marshall's +113% was a mere blip compared to the monstrous +623% put up by the Big Unit as we marched toward the World Series, it was enough to lead all Arizona pitchers this year. There's a couple of reliever stats called Shutdowns and Meltdowns: the former is an appearance where a reliever improves his team's WP by +6% or more; the latter is the reverse, dropping it by the same. This year, Marshall and Addison Reed had similar numbers: 25/10 for Marshall, compared to 26/10 for Reed. But overall, Reed was down at -97%: when he was bad, he was spectacularly so, as his 1-7 record indicates.

Elsewhere on the list, Bronson Arroyo came in second to Marshall, at +86%, with Joe Thatcher (+77%) just edging out Chase Anderson (+76%) for third-place. Down at the nasty end of the spectrum Reed, while poor, wasn't bad enough even to break into the top three. In increasing order of suck, we find Will Harris (-148%), Mike Bolsinger (-163%) and, leading the pack by almost the same again, Trevor Cahill, who racked up a startling -321% of Win Probability, in barely 110 innings of work. His 17 starts were worth an average of -14.4%, and only three were above +2.5%. There's good reason why Diamondback fandom braced itself, whenever Cahill took the mound.

Next time up, we'll look at the best and worst games of the season, and maybe even break it down to the best and worst individual plays.