Seattle Mariners vs. Cleveland Guardians

Platform comparison

Active sub-markets

Market context

The upcoming MLB fixture between the Seattle Mariners and Cleveland Guardians at Progressive Field on 26 June 2026, scheduled for 7:10 PM ET, is the real-world event underpinning this market. The Mariners sit 41-41, leading the AL West, while the Guardians are 42-39, second in the AL Central, with both teams displaying comparable offensive output and tight pitching rotations.

Historically, markets assigning 100% probability to a single outcome in MLB games are exceptionally rare and often signal a mispricing or an unconfirmed postponement, as baseball outcomes are inherently volatile. Comparable cases from the 2025 and early 2026 seasons show that even dominant teams like the Guardians, who won 6-4 on opening night against Seattle in March, frequently lose single games due to bullpen fatigue or defensive lapses, making a 100% resolution highly suspect unless the game has already been played and confirmed.

Traders must monitor the official MLB final statistics release for confirmation of the game’s completion and outcome, as any postponement or cancellation would reset the market to 50-50. Recent form indicates the Mariners lost two straight to Pittsburgh (5-1 and 11-1) before a narrow 3-2 win, while the Guardians hold a 19-17 home record; a key catalyst is the starting pitcher announcement for the Mariners, which ESPN confirmed as pending for the 26 June slot, and any injury updates to the Guardians’ rotation, which could shift the line significantly if a ace is scratched [1][2].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Seattle Mariners vs. Cleveland Guardians on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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

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.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.

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.