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USATSI

The season's first game with postseason implications was played Sunday afternoon at Progressive Field. The Cleveland Guardians outlasted the Seattle Mariners in 12 innings (CLE 7, SEA 6) and in doing so they won the season series 4-3. Yes, the Guardians and Mariners have completed their season series with more than five and a half months to play. Weird scheduling, that is.

The Guardians rallied to tie game with two runs in the bottom of the ninth and two runs in the bottom of the 11th, then won the game when José Ramírez raced home from third on Josh Bell's weakly hit grounder in the bottom of the 12th. Here's the final play of the chaotic season series finale:

By winning the season series, the Guardians hold the postseason tiebreaker over the Mariners. MLB and the MLBPA agreed to eliminate Game 163 tiebreakers as part of the new collective bargaining agreement, so all ties are broken mathematically now. Here is the tiebreaker formula:

  1. Head-to-head record.
  2. Record within the division.
  3. Record against teams in the same league but outside the division.
  4. Record in last 81 games against league opponents.
  5. Record in last 81 games against league opponents, plus one until the tie is broken.

The Guardians won the season series and thus hold the tiebreaker over the Mariners. Nice and simple. We don't have to go any deeper than that. MLB also has tiebreaker scenarios in place for three- and four-team ties, but we'll worry about those when we have three- or four-team ties and not a second sooner.

Because they are not in the same division, there are only two scenarios in which the Guardians-Mariners tiebreaker would make a significant difference:

  1. They each win their divisions and tie for the second best record in the AL. In that case the Guardians would get the bye and the Mariners would have to play in the Wild Card Series.
  2. They tie for the third and final wild-card spot. In that case the Guardians would go to the postseason as the third wild-card team and the Mariners would go home.

The Guardians and Mariners could also finish in a tie for the league's best record, or the first or second wild-card spot, but in that case the tiebreaker would only decide seeding. It's much lower stakes. For what it's worth, FanGraphs projects just a one game difference between the Guardians and Mariners this season.

As a reminder, the tiebreaker did come into play last season. The Atlanta Braves and New York Mets finished with identical 101-61 records, but Atlanta won the season series and thus the NL East, and got to skip the Wild Card Series. The Mets had to play in the Wild Card Series, which they lost to the San Diego Padres.

The Guardians took three of four from the Mariners at T-Mobile Park in the first series of the season last weekend. The Mariners were twice a few outs away from answering back with a three-game sweep in Cleveland this weekend, but the Guardians rallied to win Sunday to clinch the season series and the tiebreaker.