NCAA Tournament Upsets
Perhaps the two most discussed topics every year when analyzing the NCAA Tournament bracket is the fact that a #12 seed usually beats a #5 seed and the fact that a #1 seed has never lost to a #16 seed.
While both situations garner a lot of media attention, neither is really that unusual when you break it down and analyze the actual probabilities.
The NCAA Tournament expanded to a field of 64 teams in 1985, so we have 22 years of tournaments with the current seeding format. In 20 of those 22 tournaments (91% of the time) a #12 seed has defeated a #5 seed in the first round.
This year there is an 87.4% chance of a #12 winning based on the current odds. Old Dominion 2 (vs. Butler) and Arkansas 2 (vs. USC) are the most likely upsets, followed by Illinois 2½ (vs. Virginia Tech) and then Long Beach State 7 (versus Tennessee). As you can see, only a Long Beach State win would be considered more than a mild upset. The other three #12 seeds (Old Dominion, Arkansas, and Illinois) are all barely underdogs at 105, 110, and 125 on the money-line.
The 87.4% chance of a #12 seed winning this season is found by multiplying the money-line odds of all four #5 seeds which comes out to 12.6% or an 8-to-1 chance that all four #5 seeds win this year, which is very close to the 22-year average.
While a #12 seed is likely to win again this year, it is even more likely that all four #1 seeds win their opening round games. In fact, a #1 has never lost to a #16 seed (88-0 SU), although there have been some close calls, including Albany’s double-digit lead versus Connecticut last year.
The mathematical chance of a #16 seed winning this season is 5% which is probably a bit higher than most people would initially think; however it becomes clear when you view the game-by-game probabilities.
The biggest favorite is Florida -28 (vs. Jackson State) who has a 99.8% chance of winning straight-up, while North Carolina -27½ (vs. Eastern Kentucky) has a 99.7% of winning outright.
The next two games are where the odds come down a bit as Ohio State -21 (vs. Central Connecticut State) has a 98.4% chance of winning, while Kansas -18½ (vs. Niagara) has a 97.1% chance of winning outright.
When multiplying the four SU percentages together we get 95.1% which is the probability of another 4-0 SU start for the #1 seeds. Overall, this means once in every 20 years a #16 should win a game, so maybe we are closer than people realize to that eventual monster upset.
Steve Merril is a documented member of the Professional Handicappers League.
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