National Bank Open: Marta Kostyuk vs Katherine Sebov

Platform comparison

Market context

Marta Kostyuk’s match with Katherine Sebov is the real-world event behind this contract, and the current market is already pricing in a Kostyuk advance. The crowd-implied probability is **100% YES**, which is materially higher than the kind of gap usually seen between a clear favourite and an underdog; on form and ranking, that bias is easy to explain, with Kostyuk listed at world No. 11 on the tournament page versus Sebov at No. 231.[9]

The historical frame points the same way. The pair have already met once on the WTA main tour, on hard court in Chicago in 2021, and Kostyuk won that match in straight sets.[1][2][5] Available head-to-head and form databases also show Kostyuk with the stronger 2026 record and a much higher level of week-to-week consistency, while Sebov’s profile is closer to a lower-ranked home player trying to stretch into the main draw.[1][4][16] That makes the contract’s current pricing look more like a near-certainty than a straightforward handicap market, with no obvious analyst consensus data suggesting a meaningful disagreement against Kostyuk.[3][17]

For traders, the main catalysts are procedural rather than tactical: official match status, any reshuffling of the Toronto order of play, and whether the contest starts before the settlement deadline. The National Bank Open’s live results page has already been updating this pairing, which implies the decisive variable is completion, not mere scheduling.[13][18] Because the contract resolves to **50-50** if the match is cancelled, tied, or delayed beyond seven days without a winner, any weather interruption, withdrawal, or walkover scenario matters almost as much as pre-match strength.[13]

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 PolyGram, which mirrors the Polymarket order book directly.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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.

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.

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 PolyGram trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.