Last month, we added Championship Leverage Index (cLI) and Championship Win Probability Added (cWPA) to Baseball-Reference. These stats measure how much of an impact each player had on their team's chances of winning the World Series. Today, we are launching the Pivotal Play Finder, which measures the impact that each individual play had on a team's World Series win probability. This tool allows you to customize your query using a number of different filters to find the most impactful plays in a given situation.

It's not surprising to see that the most pivotal play in MLB history occurred in Game 7 of the 1960 World Series. But many would be shocked to find out that it was not Bill Mazeroski's walk-off (which is 6th all-time). The most pivotal play actually occurred an inning earlier. In the bottom of the 8th inning with 2 outs, the Pirates were down 7-6 with runners on the corners when Hal Smith put his team up by two runs with a 3-run home run. This play increased the Pirates' chances of winning the World Series from 30% to 93%. Unfortunately for Smith, the Yankees erased the lead in the top of the 9th, and then Mazeroski became the hero.

With the Pivotal Play Finder, you can search by event type and find out that Babe Ruth's caught stealing to end the 1926 World Series was the most impactful caught stealing in MLB history (10.22%), or that Fred Snodgrass' muff in the 1912 World Series was the most critical error in history (24.39%).

We can also search for plays involving a particular player. Derek Jeter was involved in many memorable moments during his career, but none more pivotal than his walk-off home run in Game 4 of the 2001 World Series.

We can drill down even further and search by team to see that Randy Arozarena's home run off Lance McCullers Jr. in Game 7 of the 2020 ALCS was the most pivotal home run in Tampa Bay Rays history.

In addition to sorting by Championship Win Probability Added, we can also sort by Championship Leverage Index to find the most crucial moments. These situations are usually the most pressure-packed because the difference between an out and a run has an enormous impact on a team's World Series win probability. The situation with the highest cLI in MLB history came in Game 7 of the 1962 World Series. In the bottom of the 9th inning, the Giants were down 1-0 with 2 outs and runners on 2nd and 3rd with Willie McCovey at the plate. A hit would likely tie or win the game (and World Series) for the Giants, while an out would mean a championship for the Yankees. As we know, McCovey lined out sharply to Bobby Richardson to end the series.

Please note that at the time of this writing, Regular Season event data is complete back to 1973, mostly complete back to 1950, and somewhat complete back to 1916. Postseason event data is complete back to 1903. Please see the data coverage page for details.

Just in time for the 2020 postseason, Baseball-Reference has added championship win probability added (cWPA) and championship leverage index (cLI) to the site.

Just as single-game win probability added (WPA) measures how a player impacts their team's chances of winning a game, cWPA measures how a player impacts their team's chances of winning the World Series. Similarly, championship leverage index uses the same concept of single-game leverage index (LI), but expands the scope to measure the importance of a particular play, in how it impacts a team's chances of winning the world series.

These stats are highly dependent on context and are best used as "story stats" rather than determining which player was better. When telling the story of the history of baseball, we point to the greatest moments such as Bobby Thomson's Shot Heard 'Round the World, Bucky Dent's home run over the monster, David Freese's clutch performance in Game 6, or Madison Bumgarner's Game 7 performance. Moments like these are captured in cWPA and cLI, but it's not just history's greatest moments. Every event in our play-by-play database has a value.

How are cWPA and cLI calculated?
Let's look at Bobby Thomson's Shot Heard 'Round the World for example. This was the third and final game of the National League tiebreaker series. A win for the Giants would clinch the pennant with a 50% chance of winning the world series. However, a loss would end their season, meaning a 0% chance of winning the world series. The difference between a win and a loss in this game is 50%. To get the championship leverage index, we simply divide .5 by our baseline of .006 (The baseline is explained here). This means that the Giants' cLI for the game is 83.33 (.5/.006). The LI for Bobby Thomson's final at-bat was 4.74. To get the cLI for the at-bat, we simply multiply the game cLI by the at-bat's LI, which gives us 395.0 (83.33*4.74). This mean's that this at-bat is 395x more important to the Giants' chances of winning the world series than the average play on opening day.

When Thomson stepped to the plate, the Giants were down 3-1 with 1 out in the bottom of the 9th, giving them just a 29% probability of winning the game at the start of the at-bat. Since the home run ended the game, the probability of winning the game at the end of the at-bat was 100%. To get the cWPA for the play, we multiply the difference between game win probability at the start and end of the at-bat by the difference between the championship win probability of a win and a loss. This gives Thomson .355 cWPA ((1.0 - .29) * (.5-0)). This means that Thomson's home run increased the Giants' probability of winning the world series by 35.5 percentage points. On the flip side, the opposing pitcher Ralph Branca is given -.355 cWPA for the play.

Note: cWPA values are displayed in percentage format, so the example above displays as 35.5%.

There are currently a number of places to find cWPA and cLI on Baseball-Reference:
Regular Season Leaderboards: Career Regular Season Batting Leaders
Postseason Leaderboards: All-Time Batting Leaders
Batting and Pitching Game Logs: Yaz's amazing 1967 season
Batting and Pitching Win Probability Tables: Sandy Koufax's Pitching Win Probability
Postseason Series Pages: 1991 World Series
Box Scores: 1960 World Series Game 7
League Batting and Pitching Win Probabiliy Pages: 2020 MLB Batting cWPA
Team Batting and Pitching Win Probability Tables: 1975 Reds Batting
Team Schedules: 1978 Yankees

If you have any questions or feedback on this new feature, feel free to contact us through our feedback form.

In previous months, we have launched Stathead Baseball, Stathead Hockey and Stathead Basketball. Today, we're thrilled to announce that Stathead Football has joined our suite of Stathead tools, the most powerful set of sports research tools available to the public. In fact, they're so good that the pros (whether they're running teams or covering them) also swear by them.

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In February Basketball-Reference added a list of every Game-Winning Buzzer-Beater in NBA history. Today, we're happy to announce that we've also added a list of every Game-Winning Buzzer-Beater in ABA history.
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Sports Reference LLC has acquired the Baseball Gauge from owner Dan Hirsch. Dan was hired as a developer by Sports Reference in 2018 and has spearheaded our work on fbref.com. This week, Dan migrated the MLB.TV dashboard from the Baseball Gauge to a new home on Baseball-Reference.com. Work is continuing on the migration of additional features like Championship Probability Added and Championship Leverage Index.

Following the re-launch of these features on Baseball-Reference.com, The Baseball Gauge will be shut down. You can follow Dan on Twitter.

Thanks to work from summer intern Amy Huddell and the research of APBR President Emeritus Robert Bradley, Basketball Reference has greatly expanded its database of gap years for NBA players. Specifically we've added 704 new records in addition to the previous gap year data we had on the site. This includes mid-season career interruptions, first-season injuries and situations where they were still on the roster for their final season but did not play.

Often mid-season career interruptions are injury-related, such as Derrick Rose's ACL in 2012-13 or Greg Oden's various knee ailments. Occasionally there are other reasons like Robert Reid in 1982-83 voluntarily retiring to pursue the ministry or Red Morrison in 1956-57 who went into the construction business before making a return the next season. There are a couple of players such as Charlie Paulk and Dick Rosenthal who had gap years due to military service.

Notable end-of-career notes that we've added include Wilt Chamberlain sitting out his final year under contract with the Lakers and Alex Groza being suspended indefinitely for his involvement in the CCNY point shaving scandal.

Another gap year situation is players in international leagues between getting drafted and making their NBA debut, or players extending their careers internationally. Recent examples of this that were added in this batch include Patrick Beverley and Stephon Marbury.

We hope that adding this context to player pages helps people browsing the site understand their careers a little better. Thanks again to Amy Huddell and Robert Bradley for their help with this project. If you have any questions or suggestions, feel free to contact us through our feedback form.

Today Basketball Reference is excited to announced the debut of the most powerful set of publicly available research tools on the hardwood. We're calling it Stathead Basketball and you can sign up for a free month of access here. Most of these tools may be familiar to some of our users from the Play Index. But Stathead also comes with the first of what will be many new additions: The Player Quarter Finder, which allows users to find the best performance in a quarter, or groups of quarters, since 1996-97.
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The 2020 WNBA season will begin this weekend, and Basketball Reference continues to bolster our coverage of this league, this time with the addition of player splits. This includes splits by season as well as career splits, accessible from any player's main page. Using Emma Meesseman's career splits as our example, you can see this includes home/road splits, starter/reserve splits performance in wins vs. losses, results by opponent, days rest, and breakdown by minutes played in the game.

Another smaller addition we've made is adding a stat summary to the top of player pages, giving you a quick look at the player's stats for their entire career and their most recent season. We plan to keep working on expanding our WNBA coverage, and we hope you check in with us as you follow the 2020 season! If you have any questions or suggestions, feel free to contact us through our feedback form.

As we were getting ready for 2020 Opening Day, the hard workers at Retrosheet announced their latest update, and we have gotten that new information added to Baseball-Reference as well as our Stathead Baseball tools. The highlight from the latest Retrosheet update is the addition of box scores from 1901 to 1903. This means that we now have box scores for every game in American League history, as the AL's first season was played in 1901. Retrosheet has also uncovered play-by-play accounts for games in 1916 and 1917, extending PBP coverage two more years back, although we should note 100% coverage remains limited to 1973-present. The new play-by-play allows us to further bolster our historical splits and event data.

With game log coverage back to 1901, we now have game logs for the entire careers of Hall of Famers Johnny Evers, Joe Tinker and Mordecai "Three Finger" Brown. We also now have the box score for Christy Mathewson's first no-hitter of his career, on July 15, 1901. Our Stathead Game Finder tools can now search back to 1901 as a result, and Mathewson appears as the 3rd pitcher in that time span to throw a no-hitter before their 21st birthday. Batting and Pitching Event Finder searches have been opened up back to 1916. Of the games we have PBP for in 1916 and 1917, Bill Hinchman leads with 3 walkoff hits in that span. Advanced stats tables that rely on play-by-play will also be extended back to 1916.

If you have any questions about our data coverage, you can always see it here. We're happy to have this new data on our sites and hope you enjoy it as well. Please let us know if you have any comments, questions or concerns.

And thanks again to Retrosheet!

Thanks in part to work from our intern Ryan Sullivan, College Basketball Reference now has starter and reserve designations for all NCAA Tournament games back to 1977. We previously could only claim 100% starter/reserve data back to 1994. Of course, this supplements our Final Four starter/reserve data which is already complete back to 1955. This data can be searched in our NCAA Tournament Player Game Finder.

Some searches that can be updated with these additions:

- Sean Higgins joins the list of reserve players with 30 points in a game, reaching that mark in the Elite Eight of the 1989 NCAA Tournament. He also joins the list of players with 100 points off the bench in their tourney careers.

- Reggie Theus is one point shy of Donte DiVincenzo for most points scored as a reserve in a single tournament, in 1977 with UNLV.

We hope you enjoy this addition to the site. Please let us know if you have any questions or comments.