Instead of making a post about mid-season awards, which we are sure to see a few of during the All-Star break, I figured I’d try something different. Let’s take a look at how individual plays affect a team’s postseason probabilities.

Top Plays

Earlier in the season, I added a page that shows the top plays of the season in terms of win probability added. While placing a value on the importance of the individual game is interesting, we can take it one step further and look at how each play impacts a team’s playoff probability. A big hit in a game between two teams that are not in contention will have little to no effect. But a walk-off home run in a game between teams tied for the lead in a division will have a much greater impact. So let’s take a look at the biggest plays of the first half.

This list is sorted by championship win probability added (cWPA). Just as in-game win probability added shows the change in win probability in terms of percentage points, cWPA shows the change in World Series win probability. Your first thought upon seeing the cWPA values is probably how small they are. In fact, every play this season has a cWPA of less than 1 percentage point. This shows just how little of an impact, even the most important play of the first three months of the season, has on a team’s chances of winning the World Series. Another way to look at these numbers is to multiply them by 8, to see the change in probability of being one of the final 8 playoff teams.

1) Leonys Martin’s walk-off HR (0.71 cWPA)

With two outs and a runner on 2nd in the bottom of the ninth and his team down by a run, Martin fell behind in the count 1-2 on three Ryan Madson changeups. On the fourth pitch, Madson went changeup again and Martin deposited it into the right field bleachers. The walk-off increased the Mariners in-game win probability by 86 percentage points, but more importantly, it increased the Mariners probability of winning the World Series by 0.71 percentage points.
On a side note, this play is also 40th on our list, as it decreased the A’s World Series win probability by 0.38 percentage points. The change in percentage points is bigger for the Mariners since the game was of more importance, as they were ahead in the division by 1.5 games, while Oakland was 7 games back.

2) Salvador Perez’s go-ahead 2-R HR (0.63 WPA)

In the bottom of the 8th inning with two outs, Bryan Shaw was looking to send the game to the 9th with his team up by a run. He was facing Salvador Perez, who was 1 for 12 in his career vs Shaw. But on the 1st pitch, Perez gave the fans in left field a souvenir and his team the lead. This play decreased the Indians World Series win probability by 0.63 percentage points. You can actually see the moment when Bryan Shaw realizes that pitcher vs batter stats are too small of samples to trust.
This play is also 6th on our list, as it increased the Royals World Series win probability by 0.59 percentage points.

3) Ian Desmond’s go-ahead 2-R HR (0.62 cWPA)

The next two plays on this list are from the same crazy game in Oakland. The A’s were one out away from victory with Ryan Madson on the mound, when Ian Desmond gave Texas the lead with a 2-run HR off a changeup. This play increased the Rangers chances of winning the World Series by 0.62 percentage points. As Desmond rounded the bases, Rangers announcer Tom Grieve noted that Madson threw one too many changeups, which seems to be a recurring theme here.
This play is also 24th on this list, as it increased Oakland’s World Series win probability by 0.41 percentage points.

4) Khris Davis’s walk-off grand slam (0.61 cWPA)

The next half-inning, Texas closer Shawn Tolleson intentionally walked Josh Reddick to load the bases with one out. Next, Danny Valencia flew out to shallow right, which brought up Khris Davis, who had already hit two home runs in the game. Davis then ended the game on a walk-off grand slam, which left Adrian Beltre wondering “what the hell just happened”.
From the A’s perspective, this play is 27th on the list, as it decreased their World Series win probability by 0.40 percentage points.

5) Yasiel Puig’s walk-off single and error by Michael Taylor (0.60 cWPA)

Puig’s single would have put runners on 1st and 2nd with one out in the inning, but it was Taylor’s gaffe (and Puig’s hustle) that allowed both runners to score. This was the culmination of Michael Taylor’s horrendous game, where he also struck out in all five of his at bats. If you look close enough, you can see him calculating the cWPA in his head.

Here are the rest of our top 25 plays of the first half:

Rk	Date	Play	Team	VS	cWPA	Highlight
6	6/14	Salvador Perez HR	KC	CLE	+0.59	Video
7	5/21	Matt Wieters HR	BAL	LAA	+0.58	Video
8	7/08	Luis Valbuena HR	HOU	OAK	+0.56	Video
9	6/22	Yasiel Puig little league HR	WAS	LAD	-0.56	Video
10	6/12	Jayson Werth Single	WAS	PHI	+0.56	Video
11	5/14	Albert Pujols HR	SEA	LAA	-0.52	Video
12	6/05	Matt Wieters 1B	BAL	NYY	+0.47	Video
13	7/07	Troy Tulowitzki 1B	TOR	DET	+0.47	Video
14	4/12	Geovany Soto HR	OAK	LAA	+0.45	Video
15	5/20	Melvin Upton HR	LAD	SD	-0.44	Video
16	5/10	Ryan Rua HR	TEX	CHW	+0.43	Video
17	4/12	Geovany Soto HR	LAA	OAK	-0.43	Video
18	4/08	Starling Marte grand slam	PIT	CIN	+0.42	Video
19	4/08	Starling Marte grand slam	CIN	PIT	-0.42	Video
20	6/24	Adam Lind HR	STL	SEA	-0.42	Video
21	5/21	Jayson Werth GIDP	WAS	MIA	-0.42	Video
22	5/28	Drew Butera 2B	CHW	KC	-0.41	Video
23	6/23	Adonis Garcia HR	NYM	ATL	-0.41	Video
24	5/17	Ian Desmond HR	OAK	TEX	-0.41	Video
25	6/11	Prince Fielder HR	SEA	TEX	-0.41	Video

Most Critical Moments

We can measure the importance that a particular play has on a game by using leverage index (LI), but this is limited to the situation in the game and it treats all games the same. Just as with WPA and cWPA above, we can take this one step further and measure the importance of the game by including the game’s championship leverage index (CLI). This number shows the importance of the game for each team, where the average game equals 1. If a win or a loss has a significant effect on the team’s playoff probability, the CLI will be greater than 1. By multiplying the LI and CLI, we can measure the importance that a play has on a team’s playoff probability. We’ll call this number pCLI (for championship leverage index by play). This number can be read as “how many times more important this situation was compared to the average play on opening day”.

Below are the top 10 most critical situations of the first half. As with the list above, some plays will appear twice, since they were important to BOTH team’s playoff chances.

Rk	Date	Team	Inning	Outs	Runners	Score	pCLI	Outcome	Highlight
1	5/17	TEX	Bot 9	2	Loaded	5 – 4	15.4	Khris Davis grand slam	Video
2	6/12	WAS	Bot 9	2	Loaded	4 – 3	14.2	Jayson Werth 1B	Video
3	6/05	WAS	Bot 9	2	Loaded	10 – 9	14.1	Ivan de Jesus fly out
4	6/24	TOR	Top 9	2	Loaded	2 – 3	12.7	Michael Saunders pop out	Video
5	6/11	SEA	Bot 11	2	1st & 2nd	2 – 1	12.5	Kyle Seager fly out
6	5/17	TEX	Bot 9	1	Loaded	5 – 4	12.2	Danny Valencia fly out
7	7/07	TOR	Bot 8	2	Loaded	4 – 3	12.1	Troy Tulowitzki 1B	Video
8	6/11	TEX	Bot 11	2	1st & 2nd	2 – 1	12.0	Kyle Seager fly out
9	6/11	SEA	Bot 10	2	Loaded	1 – 1	11.8	Ketel Marte fly out
10	5/06	BOS	Top 9	2	Loaded	2 – 3	11.7	Hanley Ramirez strikeout
11	6/10	SFN	Bot 9	2	1st & 2nd	3 – 2	11.5	Brandon Crawford strikeout	Video
12	7/06	HOU	Top 9	2	Loaded	8 – 9	11.5	Dae-Ho Lee strikeout	Video
13	6/10	LAN	Bot 9	2	1st & 2nd	3 – 2	11.5	Brandon Crawford strikeout	Video
14	6/11	TEX	Bot 10	2	Loaded	1 – 1	11.3	Ketel Marte fly out
15	6/05	WAS	Bot 9	1	Loaded	10 – 9	11.1	Zack Cozart strikeout
16	6/05	BAL	Bot 8	2	Loaded	1 – 0	10.9	Matt Wieters 1B	Video
17	6/05	BOS	Bot 9	2	1st & 2nd	5 – 4	10.9	Marco Hernandez strikeout	Video
18	6/30	NYN	Top 9	2	Loaded	3 – 4	10.8	Javier Baez pop out	Video
19	6/18	TOR	Top 9	1	Loaded	2 – 4	10.6	Josh Donaldson GIDP
20	6/21	BAL	Bot 8	2	Loaded	7 – 6	10.6	Adam Jones ground out

If we revisit these lists at the end of the season, there is a good chance it will be dominated by second half plays. The reason for this is, just as the most important plays happen in the later innings of the game, the most important games occur near the end of the season. However, 2016 may be different since 5 of the 6 division leaders currently have at least a 5 game lead, which may lead to less enjoyable divisional races. For the sake of exciting plays and games, let’s hope some of these leads shorten.