Seattle Mariners vs. Athletics

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Active sub-markets

Market context

The Mariners travel to Oakland on 25 May for an evening matchup against the Athletics, with the 52% implied probability favouring Seattle. Recent form has shifted slightly in the Mariners' direction following their series against Texas, where they demonstrated improved offensive consistency. The Athletics have struggled with roster depth issues throughout May, with several key contributors managing injuries that limit their ability to sustain competitive at-bats across nine innings.

Historical matchups between these AL West rivals show the Mariners have won approximately 54% of contests over the past three seasons when playing in Oakland, a marginal but consistent edge that aligns closely with the current market probability. The Athletics' home-field advantage has eroded considerably this season due to personnel gaps rather than environmental factors. Comparable May fixtures from 2024 saw the Mariners prevail in similar situations where Oakland fielded a depleted lineup.

Traders should monitor starting pitcher announcements, which typically confirm 24 hours before first pitch. The Mariners' rotation health remains intact, whilst Oakland has rotated through several spot starters due to injury management. Weather conditions at Oakland Coliseum—notably wind direction affecting fly ball distances—could influence run-scoring patterns. Any late-breaking roster moves, particularly regarding the Athletics' outfield availability, would warrant reassessment of the current probability, though no significant changes have emerged in the past 48 hours.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). The odds column is filled only where we have clean data — that avoids the made-up numbers that get a network demoted when search engines cross-check against the source venue.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

On PolyGram, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does it cost to trade on PolyGram?

Zero. PolyGram routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.