The Gap #2: the book and the crowd disagree on O'Malley, Sean vs Zahabi, Aiemann

This week's scan found twelve markets where the crowd's implied probability sits meaningfully above what the book is pricing — here is where the gaps are real and where they are not.

The fights

The largest gap in this entire dataset sits in the UFC cage. Polymarket has Aiemann Zahabi beating Sean O'Malley at 24.5%, while Stake's vig-stripped implied probability is only 21.3% — a 3.2-percentage-point gap. In money terms, the crowd's fair price on Zahabi is 4.08, and Stake is posting 4.50. That is the same fighter, the same outcome, roughly 42 cents of extra decimal odds sitting there before the card goes live on 15 June. Prediction-market traders are not always sharp, but a gap this size on a named underdog is worth taking seriously rather than dismissing.

Two other fights on the same card show smaller but still credible gaps. Kyle Daukaus to beat Bo Nickal carries a 2.7pp discrepancy — Stake's clean number is 24.7% against the crowd's 27.4%, translating to a book price of 3.90 versus a fair price of 3.64. Further down the card, Michael Chandler to beat Mauricio Ruffy shows a 2.5pp gap, with Stake pricing him at 6.40 while the crowd implies fair value at 5.72. Both are underdogs, both are priced generously relative to where the market sits. Neither gap is as clean as Zahabi, but neither should be waved away.

The football

With the World Cup in full swing, the football section dominates this issue by volume. Japan against Tunisia on 21 June produces the largest football gap at 3.0pp — Polymarket has Japan winning 55.3% of the time, Roobet's stripped number is 52.4%, and crucially both the book price and the crowd fair price land at 1.81. That is worth noting: the gap in probability is real, but when expressed in decimal odds both figures round to the same number, which tells you the actual pricing advantage is at the thinner end of that gap. Still a legitimate read, just not as dramatic as the raw percentage implies.

Brazil against Haiti (2.8pp) and Spain against Cape Verde (2.6pp) both show the crowd assigning meaningfully higher win probabilities than the books — 90.4% versus 87.6% for Brazil, 89.5% versus 86.9% for Spain. These are heavy favourites at odds of 1.08 and 1.10 respectively, so even a genuine gap of 2-3pp does not produce much return per unit. The mathematical edge is real; the practical value of grinding it at those prices is a separate question you need to answer for yourself. Qatar versus Switzerland (2.4pp, BC.Game at 1.23) and Germany versus Curacao (2.4pp, BC.Game at 1.03) sit in similar territory — crowd-confirmed favourites where the gap exists but the absolute price gives you almost no room.

Scotland versus Morocco on 19 June is the most interesting mid-range football play. Polymarket has Morocco at 49.5% and Roobet's clean implied sits at 47.0% — a 2.5pp gap at a price of 2.02. That is the same fair value figure the crowd implies, which again suggests the gap is at the lower boundary, but at evens-territory pricing you are at least getting meaningful odds if the edge holds.

The skips

France to beat Iraq (2.0pp) and both Spain versus Saudi Arabia and Canada versus Qatar (2.3pp each) land in the zone where we call it honestly: the gap is either right at or just above the 2pp floor, the prices are short, and the margin for error is thin enough that line movement between now and kick-off could erase the difference entirely. None of them are worth acting on at current prices.

Odds move — the price on the screen when you place your bet is the only price that matters.