Boston Red Sox vs. Seattle Mariners

Platform comparison

Active sub-markets

Market context

Boston’s 5-1 win over Seattle on 20 June means the listed market should already have resolved to **Boston Red Sox** on the official final result, so a current 100% YES crowd price is consistent with a completed game rather than a live pricing view.[3][5] For platform comparison, the key point is that Polymarket-style markets typically show an implied probability, while Betfair and Smarkets usually present decimal or fractional odds that must be converted back into probability; Kalshi, by contrast, is commonly quoted in cents on a $1 contract, which makes a 100-cent price equivalent to certainty before fees and settlement mechanics are considered.

Historical framing matters because MLB markets can be distorted by schedule changes, especially when a series is reordered by rain or a doubleheader. Seattle announced that a game originally slated for 20 June was moved to 19 June, which is the kind of calendar shift that can briefly leave stale listings, duplicate matchups, or mismatched ticketing pages across venues and books.[1][4] On comparable cases, the resolution source is decisive: if the game is completed, the official final score governs; if it is cancelled with no make-up, the market can be split 50-50 under the terms given.

The main catalysts for traders are therefore administrative rather than sporting: official MLB schedule updates, confirmation that the June 20 fixture actually took place, and any platform-specific settlement notices. In this market, the practical dependency is not win probability but whether the contract has already been resolved, which is especially relevant on exchanges with different KYC reach and access rules, where one venue may still show an open order book while another has already settled or removed the event.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Boston Red Sox vs. Seattle Mariners specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. Live odds come from the Polymarket order book; the other venues' contract details are maintained manually because their APIs aren't directly comparable. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). Kalshi Alternative UK routes every trade directly into Polymarket's on-chain settlement, which is why payouts land fastest.

FAQ

Where can I trade this market with the lowest fees?

On Kalshi Alternative UK, 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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within 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.