Win expectancy and a Tiger walk-off
One of my favorite features of the box score of a game on Baseball-Reference is the Win Probability Chart. Given a particular situation during a game, such as a specific inning, score, or base-out situation, there are advanced statistics that can estimate the probability of the home team winning the game. So EVERY time a certain situation occurs during a game, win expectancy will tell you the percentage of time an average home team wins the game. This is called win expectancy.
Here’s an example: Top of the 7th inning with 1 out and nobody on base and the away team leading 6-4. 82% of the time, the away team holds on to win this game. And again, that is assuming both home and away teams are league average teams.
Single plays can completely flip the win expectancy during a game. In the play described above, say the batter hits a single, so now there is 1 out and a runner on first with the away team leading 6-4. In this situation now, the away team wins 84% of the time. The batter increased his team’s win expectancy by 2%.
B4B happened to be at the Tigers-Indians game Sunday in Detroit, which had some crazy dramatic win expectancy changes at the end of the game. Austin Jackson led off the bottom of the 9th with a triple when the score was tied at 5. At the beginning of the inning in a tie game going into the 9th, home teams win 64% of the time. With no outs and a runner on 3rd, home teams win 93% of the time. The Tigers had the meat of the order coming to the plate, so I would argue that win expectancy in this particular situation would be higher than 93%.
The sequence of events that followed in this inning turned out to be an incredible disappointment for the Tigers, with Miguel Cabrera and Prince Fielder being intentionally walked and Quentin Berry grounding into a double play to end the inning with no runs scored. When the Tigers gave up back-to-back home runs in the top of the 10th and Cleveland took an 8-5 lead, the away team was expected to win 96% of the time.
This was about the time Tigers AND Indians fans started flooding the exits. I can only assume all of these fans pay attention to win probability and knew the Tigers only had a 4% chance of winning at that point. It didn’t get much better to start the bottom of the 10th when Jhonny Peralta and Brennan Boesch recorded outs and the win probability chart would say the Tigers had a ZERO PERCENT CHANCE OF WINNING. That’s not saying the home team has never won when down 3 with 2 outs, it just means it’s so rare, that unless you wanted to include order of magnitude from your Calculus class, you just say its 0%.
After Alex Avila and Andy Dirks coaxed walks from Chris Perez, Austin Jackson doubled down the LF line to score one run and give the Tigers a 15% chance at winning. Still with 2 outs, Omar Infante hit a bloop single to score both runners and tie the game at 8. Now the Tigers had a 56% chance at winning, but you had to like their odds more than that with Miguel Cabrera coming up to the plate. As it turns out, fate would have it that he mashes a home run into the bullpen in left field. His home run was skied into the air, and perfectly caught the wind blowing out to left. What a play!
To recap, the Tigers went from having a win probability of 93% in the bottom of the 9th, to basically no chance of winning in the bottom of the 10th before scoring 5 runs with 2 outs that included a walk-off home run. As you can see in the Baseball-Reference chart above, this was a roller coaster of a game and it just so happens to be the easy answer for best game we’ve seen this season!