National Bank Open (Doubles): Jiang/Wu vs Mertens/Shnaider

Platform comparison

Market context

The doubles match between Xinyu Jiang/Fang-Hsien Wu and Elise Mertens/Diana Shnaider has been priced as a clear mismatch, with Polymarket showing Jiang/Wu around 21% and Kalshi showing them at 28% in live-style contract pricing, while outside books have generally made Mertens/Shnaider short favourites at roughly 1.26–1.28 decimal odds. That gap matters because Polymarket and Kalshi express the same view differently: Polymarket’s crowd-implied probability is already net of the market’s own buying and selling, whereas Kalshi’s displayed “chance” sits beside a separate yes-price in cents; both contrast with Betfair or Smarkets, where the trader sees exchange-style decimal odds and then has to factor in commission and local account access. [3][12][10][14]

The market’s 0% YES reading is best understood against that broad consensus rather than as a literal no-win forecast, since similar pre-match models and bookmakers have repeatedly put Mertens/Shnaider in the low-to-mid 70s, including 72–77% estimates from recent tennis prediction and odds pages. A relevant comparator on the same tournament page had Fernandez/Fernandez heavily favoured over Mertens/Shnaider at 88%, which shows how quickly doubles prices can compress when one side is perceived as stronger on serve, return quality, and established pair chemistry. [7][13][4]

What moves this market now is not much fresh form data but event administration: whether the National Bank Open schedule holds, whether the match is officially played on court, and whether any walkover, delay, or retirement changes settlement away from a normal winner. On Polymarket, the listed expiry is still eight days out, while Kalshi’s contract page shows a live contract state and a later max-payout date, so traders comparing platforms need to watch whether an exchange is quoting a resolved match, an in-play position, or a contract that can still settle 50-50 if the fixture is never completed. [3][12][11]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares National Bank Open (Doubles): Jiang/Wu vs Mertens/Shnaider specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Polymarket Alternative, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.