National Bank Open: Marta Kostyuk vs Madison Keys

Platform comparison

Market context

Marta Kostyuk’s meeting with Madison Keys at the National Bank Open is priced in the market as heavily one-sided, with the contract sitting at **98% YES** for Keys if the board is read through current crowd sentiment and the main exchange-style signal. That is materially higher than the more cautious bookmaker-style numbers in the recent preview market, where Tennis.com listed Kostyuk as a **57% projected winner**, while Sportskeeda’s betting snapshot had Kostyuk around **-145** and Keys **+110**, implying a much tighter contest than the prediction market suggests.[15][18]

Historical match-up data does support Keys as the narrower favourite, but not usually to the extent implied by a 98% price. Across the available head-to-head records, Keys leads **2-0** and both previous meetings came on grass at Wimbledon in straight sets, in 2023 and 2024.[2][5][13] That record matters, yet the surface context is important: this match is on hard court, where the pair have not built the same direct comparison, and recent form is mixed enough that professional previews do not treat the result as close to foregone.[3][13]

For traders, the main catalysts are straightforward: official match confirmation, order-of-play changes, and any delay caused by weather or scheduling at Toronto. Flashscore had the fixture listed live on 6 August 2026, which suggests it was in the day’s running order, but the contract’s settlement rules still make non-completion and postponement relevant because a match that is not played, or is delayed beyond seven days without a winner, resolves 50-50.[8][13] The key dependency is whether both players take the court and complete the result before the settlement window closes on 12 August.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Best Prediction Markets, which mirrors the Polymarket order book directly.

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

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Best Prediction Markets. 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 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 trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.