Kansas City Royals vs. St. Louis Cardinals

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Market context

The Kansas City Royals and St. Louis Cardinals are scheduled to play in St Louis on 16 May, and the market is currently priced at 100% for a Royals win. That leaves no visible uncertainty in the crowd line, so a programmatic trader would treat the only live risk as event status rather than price discovery. On recent head-to-head data, the clubs have split the broader sample unevenly, with StatMuse showing the Cardinals edging the last 10 meetings and the Royals winning four of the last five in one recent window, which is a reminder that interleague form can swing quickly even when the market is fully one-sided.

For a tooling workflow, the key checks are the official line-up and game-state feeds, the confirmed starting pitchers, and whether the contest has already been completed or suspended. MLB’s scoreboard lists both clubs with a scheduled first pitch of 7:15 PM CT, and a condensed-game entry already exists for KC@STL on 15 May 2026, implying the matchup has been played or is being processed through official post-game channels. The practical catalyst set is therefore any late correction to the official result, a postponement that pushes settlement into the reserve window, or an unlikely cancellation/tie edge case that would trigger 50-50 rather than a side resolution.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Kansas City Royals vs. St. Louis Cardinals 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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

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.

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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.