National Bank Open: Joao Fonseca vs Ben Shelton

Platform comparison

Market context

Joao Fonseca and Ben Shelton are due to meet in the National Bank Open’s fourth round, with the winner moving into the quarter-finals and Shelton defending the title he won in 2025. ATP’s preview frames it as a “huge” match-up, and Tennis.com had the pre-match projection close to even at 48% for Fonseca versus 52% for Shelton, which is broadly consistent with a 47% crowd-implied price on a binary market that settles in USDC.[1][6]

The current probability sits in the middle of the range for a rematch where surface and status pull in different directions. Shelton leads their head-to-head 1-0 after a three-set win on clay in Munich in April, but this is their first meeting on hard courts, where Shelton’s recent results and bigger serve have drawn support from preview models that give him roughly a two-thirds chance.[2][12] That leaves room for a live upset price rather than a clear favourite, especially because Fonseca has already beaten a seeded opponent in Montreal and is still in the breakout phase of his ATP level rise.[7]

For traders, the main catalysts are the final order of play, any late-court reshuffle, and whether the match starts at all, since a no-contest or a delay beyond seven days forces a 50-50 outcome under the contract terms. National Bank Open scheduling has already placed the match on Centre Court for Sunday, while Polymarket activity has shown meaningful flow in the market, with over $60,000 in moneyline volume reported and the price moving around the low-50s equivalent.[4][13] In crypto terms, USDC settles the market outcome, so wider BTC and ETH moves matter mainly through overall risk appetite rather than the tennis mechanics themselves.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically this overview focuses on on-chain pricing: Polymarket's live mid comes from the Polygon conditional-token order book and settles automatically in USDC. The other three venues — Kalshi, Betfair, Manifold — sit alongside as off-chain reference points so you can see how the contract translates across regulatory and settlement regimes.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

UK Frequently Asked Questions

Why USDC and not ETH or USDT?

USDC is the Polygon standard — audited reserves (Circle, monthly attestation), deepest order book, low gas costs. ETH volatility would distort probability quotes; USDT has thinner Polygon liquidity than USDC.

Can I use Bitcoin directly?

No, Polymarket operates exclusively in USDC on Polygon. You can bridge BTC to USDC via an exchange or bridge service and deposit on Polygon — typically 10-30 minutes processing time.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.