UFC 331 odds: five weeks flat, then seven days of movement

The UFC 331 odds board did nothing for five weeks. Then, on September 13, the prices started moving, and they have moved every day since.

I went back through our own stored line history, which samples twenty sportsbooks daily and keeps the median, to find out what actually changed. The answer is that almost nothing changed about the fights and almost everything changed about the prices, which is the most ordinary thing in the sport and also the most revealing.

Photo: Chris Hunkeler from Carlsbad, California, USA / CC BY-SA 2.0

Five weeks of nothing, then seven days of everything

Take the main event as the clean case. Joshua Van vs Alexandre Pantoja opened on August 8 at minus 117 and stayed inside a five cent window until September 12: minus 112, minus 121, minus 113, minus 117, drifting nowhere for thirty six days. Since September 13 the median has moved every single day in the same direction. Minus 126, minus 131, minus 131, minus 132, minus 135, minus 138, minus 141.

Gable Steveson vs Sean Sharaf did the same thing on a larger scale. Steveson opened at minus 1360 on August 8 and spent five weeks between minus 1390 and minus 1480, which for a line that size is a flat line. Since the 13th: minus 1567, minus 1656, minus 1822, minus 1909, minus 1975, minus 2097, minus 2175. He has gone from an 87.5 percent favorite to a 92.2 percent favorite with no fight having taken place.

Nothing on the card justifies a synchronized move. Renato Moicano vs Brian Ortega came off on September 15 and the UFC shifted every segment back thirty minutes the same day, both after the movement started, and neither touches a heavyweight or a flyweight title fight. What this looks like is books that were carrying lazy numbers while nobody wagered on them being forced to carry real ones during fight week.

The money went where our model will not follow

Here is the whole board as it stands this morning, market probability stripped of vig against what our model gives the same fighter.

Seven of the twelve land inside seven points of each other, and Edmen Shahbazyan vs Brunno Ferreira lands on 62.3 percent from both, which is the sort of coincidence you only notice because you built the table.

The interesting part is that the two fights the money steamed hardest this week are two of the five the model likes least. Steveson went from 87.5 to 92.2 percent on the board; the model has him at 83.8, below where he started. Casey O'Neill vs Eduarda Moura was minus 177 on September 1 and sat there for twelve days, then went minus 183, minus 187, minus 190, minus 205, minus 219, minus 226. The model calls that fight 53.1 to 46.9, which is another way of saying it has no idea, while the market has walked it to a two thirds favorite.

I want to be careful about what that does and does not mean. A market disagreeing with a model is not a market being wrong; the books have information the model does not, including whose camp looked bad in the last week and where the actual money is going. But a seven day, one direction move on a fight with no news attached is not information arriving. It is a price being discovered.

The two the market quietly walked away from

Photo: MMAnytt / CC BY 3.0

Two fighters got longer instead of shorter, and both are the recognizable name in their bout.

Giga Chikadze opened at plus 274 against Joanderson Brito on September 1 and held that number for eleven days. Since the 13th: plus 287, plus 294, plus 306, plus 307, plus 309, plus 320, plus 328. That is a drift of about three points of implied probability away from a former title eliminator headliner, in the week when the board was supposedly getting sharper. Our model has him at 27.3 percent, modestly above the market's 22.5, so the drift has taken the price past our number rather than toward it.

Patricio Pitbull did the same. He opened plus 182 against Dooho Choi on September 1 and is plus 223 now, which moves him from a 34.3 percent chance to a 29.8 percent one. He is 37-9 across a career that includes five Bellator title reigns, and this is the second straight fight week where the market has priced him down rather than up.

Both of those are worth flagging precisely because they run against the pattern everyone assumes. The lazy story about fight week money is that it chases names. On this card it did the opposite twice.

The three the board treats as formalities

The largest disagreements on the card are all in one direction: three fights where the market has essentially closed the book and the model has not.

Tai Tuivasa vs Robelis Despaigne is the extreme case, and we wrote about it separately. Tuivasa opened plus 365 and is plus 412 now, an 18.8 percent chance. The model has it at 53.4, a coinflip. A 34.6 point gap is the widest on this card by nearly twenty points.

Michael Aswell Jr. vs JooSang Yoo is the one nobody is discussing. Aswell was plus 211 on September 14 and is plus 172 now, one of three underdog prices on the card that came in rather than drifted out this week. Even after that move the market has him at 35.4 percent and the model has him at 51.7.

And the main event, at 56.3 against 71.9, is the third. Which means the fight the market is least sure about all week is also the one where it and our model are furthest apart at the top of the card.

Twelve fights, one board, and a week where the prices moved more than the fighters did. The bell is at 9:00 p.m. ET from Crypto.com Arena in Los Angeles and the results land here as they happen.