Here is the list of tiebreakers that matter to the Boston Red Sox through the games of September 16, 2026. If these teams ended up tied for a wild card berth or a division title, the winner of the berth is the one that holds the tiebreaker.

As you can see, the Red Sox tiebreaker with the Guardians will go to whichever team wins their 3-game series next week (to be played September 22-24). It’s a simple criterion that has a very complex explanation. An explanation that I will now give to you!

So let’s assume the Red Sox and Guardians end up tied. That could happen, for example, if the Red Sox go 3-7 the rest of the way, and the Gaurdians go 7-2, putting both teams at 85-77 on the season. Or 2-8, 6-3, putting them both at 84-78.

The first tiebreaker rule is head-to-head record. So far this season, in their 3 games against each other, the Red Sox have won 2 and the Gaurdians 1. If the Red Sox win 2 or more of their 3 upcoming games, that assures they win more of their head-to-head games against the Guardians than the Guardians do, so they win the tiebreaker based on this first tiebreaking rule.

If the Gaurdians win all 3 upcoming games, they take the tiebreaker, with a 4-and-2 record head-to-head.

If, however, the Guardians take 2 of 3 in their upcoming series, they end up 3-3 against each other, and the first tiebreaker rule doesn’t resolve the tie. So we have to go to the second tiebreaker rule.

The second tiebreaker rule makes the winner the one with the better record against their own division. So far this season, the Red Sox are 24-25 in their division, with 3 to play against Tampa Bay. The Guardians are 27-22 in their division, with 3 to play against Kansas City. Given that, the only way this second tiebreaker doesn’t resolve in favor of the Guardians is if the Red Sox sweep their 3 games against Tampa Bay, and also the Guardians are swept in their 3 upcoming games against Kansas City. But that would mean the Red Sox went 4-2 in their games against Cleveland and Tampa Bay, and Cleveland went 2-4 in their games against Boston and KC. That’s too many Red Sox wins combined with Guardians losses (8) for the Red Sox and Guardians to end up tied in the first place. They can only end up tied if the combination of Red Sox wins and Guardians losses is 5. In other words, if the Red Sox and Guardians end the season tied, then either the Red Sox didn’t sweep Tampa Bay, or the Guardians were not swept by Kansas City, or both. Therefore, if this second tiebreaker does come into play, it will go in favor of the Guardians.

And that means, if the Guardians win 2 of 3 games in their upcoming series with the Red Sox, forcing the second tiebreaker rule to be used to decide any potential tie, the Guardians hold the tiebreaker.

So there you have it. If the Red Sox win 2 or more against the Guardians next week, the Red Sox hold the tiebreaker; if the Guardians win 2 or more against the Red Sox next week, the Guardians hold the tiebreaker. The tiebreaker goes to the winner of that series.