National Bank Open: Marta Kostyuk vs Madison Keys

Platform comparison

Market context

Polymarket’s contract is pricing **Madison Keys at 57%** to advance, so the market is leaning her way but still leaving a meaningful chance for **Marta Kostyuk** under the same conditional token settlement on Polygon in USDC. For a user holding or buying YES, the live question is not whether Keys is the better-known player, but whether the market has already discounted enough of her edge.

The historical frame supports that modest favourite status. Keys has won both of their previous meetings, including straight-sets wins at Wimbledon in 2023 and 2024, and multiple head-to-head databases show a 2-0 lead with both matches on grass[1][4][6]. Rankings also tilt towards Keys, with Tennis.com listing her at WTA No. 22 and Kostyuk at No. 11 for this match, which reflects form and seeding context more than a direct forecast of the result[14]. That combination usually keeps a money-line-style market from drifting to a one-sided price unless one player has a clear surface or fitness advantage.

The main catalysts are confirmation of the match taking place as scheduled, the order of play, and any late withdrawal or retirement news. If the match is completed and a player advances, the contract resolves to that player; if it is not played at all, ends level, or is pushed more than seven days without a winner, it resolves 50-50 under the market rules. Given the current live-status coverage from tennis trackers and the fact that the match is listed for 6 August in Toronto, traders are mostly watching for whether the event proceeds normally or is disrupted by schedule changes, which can matter as much as pre-match form in a single-elimination tennis market[5][14].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track National Bank Open: Marta Kostyuk vs Madison Keys 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

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 PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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 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.