The case for the postseason NRFI writes itself. The best starters in baseball, on full rest, in cold air, in games where every run is managed like it is the last one. It sounds like a scoreless first inning waiting to happen, and the price at the window usually agrees.
We counted. Every postseason game from 2015 through 2025 with a completed first inning, 440 of them, from the MLB Stats API, beside the 25,227 regular-season games of the same eleven seasons. The October first inning is not quieter than the summer one. If anything it is a little louder.
The headline number
| Scoreless 1st | Rate | |
|---|---|---|
| Regular season, 2015-2025 | 12,493 of 25,227 | 49.5% |
| Postseason, 2015-2025 | 206 of 440 | 46.8% |
| Postseason without the 2020 bubble | 180 of 387 | 46.5% |
The 95% interval on the postseason rate runs from 42.2% to 51.5%. That interval contains the regular-season figure, so the honest reading is “no evidence October is different,” not “October is worse.” What the interval does not contain is anything like the 55% to 60% the ace-versus-ace story implies.
One objection deserves an answer before going further. Playoff teams are better than average teams, so maybe their own first innings were already quieter than the league’s during the summer, and the postseason number is a fair reflection of that. We checked. For each postseason game we took the two clubs’ regular-season NRFI rates from that year and combined them into a game-level expectation. Across all 440 games that baseline comes out to 49.5%, the same as the league. Playoff clubs do not carry an unusually quiet first inning into October, and they do not find one there.
Season by season
| Season | Regular season | Postseason |
|---|---|---|
| 2015 | 1,196/2,433 (49.2%) | 16/36 (44.4%) |
| 2016 | 1,162/2,429 (47.8%) | 17/35 (48.6%) |
| 2017 | 1,139/2,430 (46.9%) | 20/38 (52.6%) |
| 2018 | 1,209/2,433 (49.7%) | 16/33 (48.5%) |
| 2019 | 1,153/2,433 (47.4%) | 12/37 (32.4%) |
| 2020 | 449/900 (49.9%) | 26/53 (49.1%) |
| 2021 | 1,208/2,437 (49.6%) | 15/37 (40.5%) |
| 2022 | 1,259/2,431 (51.8%) | 22/40 (55.0%) |
| 2023 | 1,212/2,437 (49.7%) | 19/41 (46.3%) |
| 2024 | 1,295/2,430 (53.3%) | 19/43 (44.2%) |
| 2025 | 1,211/2,434 (49.8%) | 24/47 (51.1%) |
Four postseasons landed above their regular season and seven below. A single October is 33 to 53 games, so any one of these rows is noise. 2019 at 12 of 37 is the kind of thing that happens to a coin. The pooled figure is the one to hold onto.
By round
| Round | Scoreless 1st | Rate | Runs in the 1st, per game |
|---|---|---|---|
| Wild Card | 34 of 67 | 50.7% | 0.94 |
| Division Series | 87 of 181 | 48.1% | 1.07 |
| LCS | 54 of 126 | 42.9% | 1.25 |
| World Series | 31 of 66 | 47.0% | 1.03 |
The League Championship Series is the loudest first inning in the data, and the one where the “best pitching in baseball” story should be strongest. The intervals on these rows are wide, 35% to 52% for the LCS, so read the table as “nothing here supports the story,” not as a ranking.
What changes is the shape of the inning
Postseason first innings are not producing more crooked numbers. They are producing more single runs.
| Runs in the 1st | Regular season | Postseason |
|---|---|---|
| 0 | 49.5% | 46.8% |
| 1 | 22.2% | 25.5% |
| 2 | 13.1% | 13.6% |
| 3 | 7.8% | 7.7% |
| 4 or more | 7.4% | 6.4% |
That is what you would expect from October baseball as it is actually played: leadoff hitters who work counts, a sacrifice or a stolen base in the first, a manager who will trade an out for a run in the third inning of a series, let alone the first. Big innings are slightly rarer. One run is more common. For an NRFI, one run is all it takes.
The split that is real: the clock
The one cut of this data that does not look like noise is the start time.
| Start, Eastern | Postseason | Regular season |
|---|---|---|
| Before 3 pm | 24 of 38 (63.2%) | 2,604 of 5,241 (49.7%) |
| 3 to 5 pm | 40 of 74 (54.1%) | 1,773 of 3,590 (49.4%) |
| 5 to 7 pm | 27 of 51 (52.9%) | 894 of 1,730 (51.7%) |
| 7 pm or later | 115 of 277 (41.5%) | 7,222 of 14,666 (49.2%) |
Collapse it to MLB’s own day and night flag and the postseason splits 87 of 155 (56.1%) scoreless by day against 119 of 285 (41.8%) at night. The regular season shows no such gap: 49.8% by day, 49.4% at night. If day and night postseason first innings were truly the same, a gap this size in samples this size would turn up about once in 250 tries.
The split survives every slice we tried. It holds inside every round: Wild Card 64.7% day against 36.4% night, Division Series 53.2% against 44.1%, LCS 54.3% against 38.5%, World Series 57.1% against 45.8%. It holds with the 2020 bubble removed, 54.3% against 42.7%. And it is not the weather. Night games in October are about five degrees colder than day games on average, 67°F against 73°F, and cold air favored the pitcher in the 2026 regular season. The postseason runs the other way: inside every temperature band, the day rate beats the night rate, 61.5% against 33.9% under 60°F, 63.3% against 49.3% in the 60s, 52.2% against 40.6% at 70°F and up.
We do not have a mechanism to offer for this, and we are not going to invent one. Afternoon shadows between the mound and the plate are the usual October explanation for quiet bats, but the quietest bucket in the table is the one that starts before 3 pm, ahead of the shadows. Whatever it is, we found it by cutting the data several ways, and a pattern found that way earns a smaller claim than one you predicted in advance. Treat it as the strongest lead in the postseason data, not as a rule.
Temperature, for the record
| Postseason, open air | Scoreless 1st |
|---|---|
| Under 55°F | 15 of 32 (46.9%) |
| 55 to 64°F | 37 of 90 (41.1%) |
| 65 to 74°F | 52 of 113 (46.0%) |
| 75°F and up | 52 of 101 (51.5%) |
| Dome or roof closed | 50 of 104 (48.1%) |
The regular-season cold effect does not reproduce in October. The coldest games are mostly night games, and the night effect is the one that dominates.
What this does to the price
None of this is a recommendation. It is arithmetic. A first-inning market priced at −130 needs the scoreless side to hit 56.5% of the time to break even, and at −120 it needs 54.5%. The postseason rate across eleven Octobers is 46.8%. Even the day-game rate, 56.1%, sits at the break-even line rather than above it. A postseason NRFI price that has been shaded toward the pitchers is pricing a story the first inning has not been telling.
What we are doing with it
The board runs through the postseason with the same two models and no October adjustment, because 440 games is about three weeks of a regular season and we do not tune a model to three weeks. We will keep counting the day and night split as this postseason plays out, and if it is still there next spring it goes in the model with its own denominator.
Method
Every game of type Wild Card, Division Series, League Championship Series, and World Series from 2015 through 2025, pulled from the MLB Stats API schedule endpoint with linescore hydration, kept when the game was Final and the first inning was recorded: 440 games. The same pull for regular-season games in those seasons: 25,227 games. 2020 is included; removing it moves the postseason rate from 46.8% to 46.5%. Day and night is MLB’s own flag. Start hours are Eastern. Temperature and roof status come from each postseason game’s live feed, with dome and closed-roof games held out of the temperature rows. The playoff-club baseline is the geometric mean of the two clubs’ regular-season NRFI rates in that season, averaged over the 440 games.