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Championship Leverage Index is the metric of choice for watching pennant race baseball

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It’s a great tool to use as the regular season begins to wind down.

MLB: Seattle Mariners at Houston Astros Thomas B. Shea-USA TODAY Sports

Championship leverage index (cLI) is one of the most underrated baseball metrics ever created. And I am not hyperbolizing. When I decide what game I would like to watch, cLI is the first number that I consider.

That’s why I’m introducing it to you, the sabermetrically inclined baseball fans.

All of you likely have a favorite team. For some of you, your team might be in the postseason race, and that’s great! For the rest of you, your team might be out, and that’s not so great. It doesn’t really matter to me — we all love baseball here, and we all have a desire to watch the most important games, regardless of whether our favorite teams are in it. Of course, I’d love to watch every game, but that’s not really possible given the amount of time that I have. That’s why we must prioritize.

With about five weeks left in the season, it’s not hard to see that some games are clearly more important than others. On Monday, the Astros and Athletics began a three-game set in Houston. With only 1.5 games separating those two at the top of the AL West standings, it’s clear that this is a crucial series. CLI confirms that belief, as the combined cLI for Monday’s game was 4.64.

But, really, you’re probably asking what is cLI, and how do I use it?

As stated above, cLI stands for Championship Leverage Index. The metric was developed about 10 years ago by Dave Studeman and Sky Andrecheck. Nightly numbers are located on the homepage of a website called The Baseball Gauge, which was started and is maintained by Dan Hirsch. (It’s an excellent website, by the way.)

What cLI measures is the importance of an individual game to a team’s World Series chances. It’s not hard to interpret. An Opening Day baseball game has a cLI of 1.00, as every team has the same 0-0 record. As we get deeper into the season, cLI intuitively increases for teams in the race and decreases for the teams well out of it (or eliminated). For example, Monday’s game between the Blue Jays and Orioles had a combined 0.00 cLI — both teams have a zero percent chance to win the World Series, so the game does not affect their chances at all. Whether the Blue Jays or Orioles win, both teams will still have a zero percent chance to win the World Series.

It’s important to know how cLI is calculated. Since it is a Leverage Index, what tells you is how much more important said game is compared to an Opening Day game. An Opening Day game affects teams’ World Series odds by 0.5869 percentage points. So, if the Athletics have a 2.44 cLI (as they did on Monday), this would mean that their game against the Astros could impact their World Series odds by as many as 1.43 percentage points. That is extremely significant.

The highest cLI possible would be for Game 7 of the World Series, as winning it would give your team 100 percent odds of winning the World Series and losing it would give them 0 percent odds. This cLI would be 170.39.

When you’re deciding which games to watch on a regular Tuesday night like tonight, consider using cLI to help you make your decision. It can help you ensure that you are watching the most exciting baseball games every single night.


Devan Fink is a Featured Writer for Beyond The Box Score. You can follow him on Twitter @DevanFink.