National Bank Open: Marta Kostyuk vs Iga Swiatek

Platform comparison

Market context

Marta Kostyuk and Iga Swiatek are set to meet at the National Bank Open in Toronto, with the market pricing Kostyuk at **36%** against an implied Swiatek edge of about **64%**. That is a narrower split than Tennis.com’s projected winner model, which has Swiatek at **57%** and Kostyuk at **43%**, suggesting the prediction market is giving Kostyuk a modestly better chance than that analyst-facing line.[3]

The broader framing is familiar for a WTA hard-court match between two seeded players: Swiatek has the stronger overall profile and leads the head-to-head **3-1**, but Kostyuk won their most recent meeting at Roland Garros in 2026, which tempers how one reads any simple favourite-longshot split.[1][7] Tournament listings also place this as a hard-court match in Toronto, where surface and recent form can matter more than the historical record alone.[1][9]

Traders should watch for three things before settlement: confirmation that the match is played within the scheduled window, any order-of-play changes, and whether either player advances or withdraws through late tournament news. The National Bank Open’s own reporting indicates Swiatek and Kostyuk were both still in the draw heading into this match, and third-party match pages list it for 8 August in Toronto, so the main non-performance risk is schedule disruption rather than a misread on the pairing itself.[10][11] If the match is delayed, abandoned, or not completed in time, the contract’s fallback rules become more important than pre-match price discovery.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track National Bank Open: Marta Kostyuk vs Iga Swiatek across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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

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 Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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.