National Bank Open: Marta Kostyuk vs Katherine Sebov

Platform comparison

Market context

Marta Kostyuk’s second-round meeting with Katherine Sebov in Toronto is being priced as a near certainty in the contract, with the market at 100% YES against a live sportsbook and form backdrop that still points strongly one way. Official tournament data lists Kostyuk as the World No. 10 and Sebov as a wildcard ranked No. 231, and their only prior tour-level meeting ended 6-0, 6-3 to Kostyuk on hard courts in Chicago in 2021.[5][8][13]

That historical frame matters because prediction markets on tennis often trade close to the practical probability of a player advancing, but this one is even more compressed than a standard favourite line. Recent comparison sites and trading screens show Kostyuk ahead by a wide margin, while bookmaker-style previews have also described her as the clear favourite; the only meaningful divergence is not on who is expected to win, but on how much room remains for volatility if the match is not completed.[3][9][15] Kostyuk’s recent Toronto results also support the favourite case: the tournament’s own match page shows she won their previous meeting this week in straight sets, 7-6(4), 6-0, after a first-set test.[2][7]

For traders, the main catalysts are administrative rather than competitive: whether the match stays on schedule, whether it is moved by rain or court timing, and whether it is finished within the settlement window. The market rules make those operational details important, because a cancellation, tie, or a delay beyond seven days would settle 50-50 rather than to either player. Live score services currently list the contest as in progress, which reduces cancellation risk but raises the usual in-play dependency on a completed result before the window closes.[1][14][16]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track National Bank Open: Marta Kostyuk vs Katherine Sebov 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

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.