Real Madrid beat Inter 2–1, the lay went down for the full €650, and the book is back to a coin flip. Tonight Arsenal are 1.70 to lay in Naples: €700 at risk to win €980.

Real Madrid won 2–1 and the position lost the whole €650. That makes four wins and four losses in eight filed days, plus €700 on €7,710 of risk: a return that has gone thirty-nine, nineteen, nine in three evenings, which is what a sample of eight does rather than what a method does. The pattern inside the losses is worth naming, though. They came at 1.84, 1.73, a straight draw at 3.20, and 1.65 — the three cheapest lays on the book are three of the four losses. That is the arithmetic of laying short prices working exactly as advertised and against us: the favourite holds more often than not, the liability goes every time it does, and €980 comes back only on the days it doesn’t.

Tonight the exchange makes Arsenal the favourite at the Maradona: 1.70 to lay, €700 at risk to win €980. That is below the 1.98 pivot, so the ordinary shape holds — a win is worth more than a loss costs. Break-even is 41.7%, and a quarter of the fair line is the draw alone, which on a lay pays in full. Strip the margin off the back column — 6.0 Napoli, 4.0 the draw, 1.69 Arsenal, an overround of 100.8% — and the fair prices read 16.5% / 24.8% / 58.7%. The two results that pay us add to 41.3%. We need 41.7%. Four tenths of a point against us, roughly €6 of negative expectation per €1,000: thin, and on the wrong side of zero, as every position this book has filed has been. The crack, such as it is: this is Arsenal’s first away night in Europe this season, they are without Saliba and Mosquera at centre-back, and a September trip to Naples is the sort of fixture that gets priced off league form rather than off the ground. The clubs have met four times, Arsenal winning three, the last two in the Europa League in 2018–19.

The honest counter is short and it is strong. Arsenal have won everything they have played — the Community Shield against Manchester City, then their opening three league matches — while Napoli are twelfth, beaten by Como and Inter, and without McTominay, Buongiorno, Marianucci and Anguissa, with Neres a doubt. The market is not pricing a hunch here, it is pricing a gap in form and availability that anyone can see, and 1.70 for a side in that condition is not a number that needs defending. We are not saying Napoli are the better team. We are saying that 58.7% is a price we would rather sell than buy, and that by our own arithmetic we are four tenths of a point short of being right about even that. Eight closed positions prove nothing, in either direction.