Dbacks Playoff Odds: Simulations, Tiebreakers and Price

A playoff percentage is a count of simulated outcomes. On FanGraphs, a team with 9% World Series odds won it 900 times across 10,000 simulated seasons, and every other column on the page reads the same way.

That framing matters when Arizona sits on the edge of the field. The figure is a frequency across seasons that have not happened, not a forecast of the one that will. FanGraphs itself tells readers to view the odds as a distribution's center, because the team ratings behind them are uncertain too.

The simulation starts from the real standings and plays only the games left. FanGraphs simulates the season 10,000 times on the actual remaining schedule, with a method adapted from CoolStandings (as described on its library page dated March 2016).

Each simulated game needs a win probability for both clubs. In the default mode, team strength comes from a 50/50 Steamer and ZiPS blend scaled to playing-time estimates, so the Diamondbacks are rated on projected talent rather than only on what they have done so far. Alternate modes swap in season-to-date stats or coin flips.

Then the schedule does its work. Every remaining series against a division rival or a wild-card contender moves two teams at once, which is why the same record can carry different odds for two clubs. It is the same logic behind NHL strength of schedule ratings: who is left on the calendar matters as much as the record.

Run differential feeds the team-strength input because it often says more about future results than the win-loss column. Clay Davenport's Baseball Prospectus study (2004) found Pythagorean record, the record a team's runs scored and allowed imply, was the better predictor of rest-of-season record until actual record took over after 140 games.

For most of a season, then, a Diamondbacks club whose run differential outpaces its record should get a better rating from a model than the standings suggest, and a club living on one-run wins should get a worse one. By late September the gap closes. Baseball Prospectus calls the winning percentage assigned to each team the most important piece of its Monte Carlo simulation, and that is exactly where the choice between run differential and record lands.

Ties are settled on paper, not on the field, so a simulation has to track every season series. Per MLB, six teams per league qualify: three division winners and three Wild Cards. When two finish level, the season series between the tied teams decides it first, and no tiebreaker game is played.

If head-to-head is even, intradivision record comes next, and MLB says that step applies even to Wild Card ties between teams that do not share a division. Intraleague record follows, and the fourth step uses intraleague records after the All-Star break rather than the exact midpoint of the season.

For Arizona in a crowded wild-card race, a model that skips these rules misprices every simulated tie. A D-backs series win over a direct rival is worth more than one game in the standings, because it can also decide who holds the spot when the records match.

A model reports a frequency; a market reports where buyers and sellers meet. On Polymarket, the displayed probability is the bid-ask midpoint, so a 37% reading sits between a 34 cent bid and 40 cent ask. When the spread is wider than 10 cents, Polymarket instead shows the last traded price (per its help page, as of March 2026), which can be stale in a thinly traded team market.

Sportsbooks add their own margin on top of the price. The breakdown of Spurs relegation odds walks through stripping that margin out to reach a fair probability, and the same step applies to a Diamondbacks futures price.

Put the model percentage next to the market's implied probability, then check three things: whether the market spread is tight enough for the price to be current, whether Arizona's run differential runs ahead of or behind its record, and which head-to-head series are left against the teams around it. The same checklist works in hockey, where Flyers playoff odds turn on points pace instead of run differential, and across the rest of our playoff odds coverage.

Do the Diamondbacks still have a chance?

Look at the model percentage: any figure above zero means Arizona reached the postseason in at least some simulated seasons of the games left. FanGraphs advises reading that figure as the center of a range rather than a fixed number, so a small percentage is a rough estimate, not a verdict.

What happens if the Diamondbacks lose today?

The game comes off the remaining schedule, the loss goes into the standings and the simulations run again on what is left. If the opponent is a club Arizona is chasing, the loss also shifts the season series, which is the first tiebreaker MLB applies between two tied teams.

Who are the favorites to win the MLB playoffs?

On a simulation model, the favorite is the club that wins the World Series in the largest share of simulated seasons. On a prediction market, it is the team with the highest displayed price, which is a midpoint or a last trade rather than a model output, so the two lists can differ.

• FanGraphs Sabermetrics Library, Playoff Odds, 2016-03-09 (accessed 2026-10-30)
• MLB.com, How to determine playoff tiebreakers, undated (accessed 2026-10-30)
• Baseball Prospectus, Playoff Odds Report, Redux: Reworking the System, 2004-09-23 (accessed 2026-10-30)
• Polymarket Help Center, How Are Prices Calculated?, 2026-03-13 (accessed 2026-10-30)