Marcus Tillman had a perfect bracket for 52 hours straight.

The 34-year-old from Dayton, Ohio entered 2023’s NCAA Tournament riding a three-year streak of top-10 finishes in his office pool. He’d studied tempo ratings, KenPom efficiency charts, and injury reports until midnight. Then a 13-seed from Furman drained a buzzer-beater to eliminate Virginia, and Marcus watched his bracket crumble in real time. “I had Virginia in the Elite Eight,” he told his coworker the next morning, phone face-down on his desk. “I do this every year. Every single year.”

Marcus isn’t alone. Here’s the stat that changes everything: since 2010, double-digit seeds have won at least one game in every single NCAA Tournament. Every one. According to NCAA tournament records compiled through 2024, 12-seeds now win their first-round matchup approximately 35% of the time. That’s not a fluke. That’s a pattern. And most bracket builders are still ignoring it completely.

The Problem With How We Build Brackets

Most people build brackets the same way. They pick the higher seed, add a sprinkle of chaos, maybe slot one Cinderella into the Sweet 16, and call it strategy. It isn’t strategy. It’s hope wearing a spreadsheet costume.

The seeding system rewards conference dominance and strength of schedule in ways that systematically obscure tempo mismatches. Teams seeded 5 through 8 often play slower, more deliberate basketball built for grinding through conference play. When a 12-seed arrives with a frenetic transition offense and nothing to lose, the matchup is more dangerous than the seed difference suggests. Way more dangerous.

When did you last seriously pick a 12-seed to go past the second round? If your answer is “never” or “once by accident,” you’re leaving real bracket equity on the table.

To understand why this matters, you need to go back to 2018. That was the year UMBC became the first 16-seed in men’s basketball history to defeat a 1-seed, dismantling Virginia by 20 points. It wasn’t luck. UMBC ranked in the top 40 nationally in adjusted offensive efficiency, per KenPom’s 2018 data. Virginia played at the second-slowest tempo in the country. The pace collision was catastrophic, and almost nobody saw it coming.

It’s not seeding that matters most. It’s tempo. It’s efficiency margins. It’s whether a team can force a 5-seed into playing at someone else’s pace for 40 minutes.

Did You Know: According to FiveThirtyEight’s 2023 bracket analysis, upsets by seeds 10 through 15 accounted for 42% of all first-round games where the favored team was eliminated. That number has trended upward since 2015.

What’s Driving the Surge in Upset Culture

Three forces are reshaping tournament basketball right now. None of them are getting enough attention.

1. Transfer portal parity. The transfer portal, fully opened in 2021, has functionally redistributed elite talent downward. Mid-major programs can now recruit players who would have previously spent four years on a bench at a Power Five school. According to a 2024 report from The Athletic, transfer portal activity increased 31% from 2021 to 2023, with mid-major programs representing the fastest-growing receiving group.

2. Tempo divergence. High-major conferences slowed down in 2023. The average possessions per game in the ACC dropped to 67.4, per KenPom’s 2023 season data. Meanwhile, several mid-majors pushed north of 72 possessions per game. That’s not just a stylistic difference. It’s a structural mismatch that makes first-round upsets more likely when these teams collide in March.

3. Three-point variance. It’s brutal and it’s real. A team that shoots 36% from three during the regular season might shoot 29% on a neutral floor or 44% because shooters get hot. One hot shooting performance from a double-digit seed can erase a 6-point talent gap completely. Researchers at MIT’s Sloan Sports Analytics Conference noted in their 2022 paper on tournament predictability that single-game three-point variance is “the single largest driver of upset probability in short-format tournament play.”

Pro Tip: Before locking your next bracket, cross-reference every 5-versus-12 and 6-versus-11 matchup using KenPom’s adjusted tempo ratings. If the lower seed plays 4+ possessions per game faster than the higher seed, treat it as a virtual coin flip. Don’t default to the seed. Do the math.

The Teams Crushing It Right Now

Nobody is talking about this — but they should be. Several mid-major programs have built rosters in 2024 that are structurally designed to exploit exactly these vulnerabilities.

St. Peter’s, who shocked Kentucky as a 15-seed in 2022 before reaching the Elite Eight, proved the blueprint works. Their adjusted defensive efficiency that season ranked 47th nationally, per KenPom. Not elite. But elite enough, combined with elite transition pace and three-point volume, to make them genuinely dangerous in a bracket.

The 2024 tournament cycle is showing similar fingerprints from programs in the Missouri Valley Conference and Atlantic Sun. Teams that rank inside the top 60 in adjusted offensive efficiency while playing at a pace above 70 possessions per game. They’re not underdogs in any meaningful analytical sense. They’re just unseeded relative to name recognition.

Would you bet your bracket entry on tempo-adjusted offense right now, even if it meant picking a 13-seed to reach the Sweet 16? The data says you probably should have done it at least once by now.

Bracket Burn: Memorize this upset pattern: When a 12-seed ranks inside the top 50 in KenPom adjusted offensive efficiency AND plays at 70+ possessions per game against a 5-seed with a sub-68 tempo rating, that 12-seed has historically won 41% of those matchups since 2015, per KenPom historical data. That’s nearly a coin flip. Stop treating it like a safe pick.

What This Means for Future Tournaments

The bracket is lying to you. Every year. Same result.

The seeding methodology hasn’t fundamentally changed to account for pace divergence, portal-driven roster reconstruction, or the increasing three-point reliance of mid-major offenses. The committee still leans heavily on metrics like RPI and record against top-25 teams. Those metrics don’t capture what happens when a 71-possession team meets a 66-possession team in a single-elimination game on a neutral floor.

Here’s what the numbers tell us: the structural conditions that produce upsets aren’t receding. They’re expanding. As the transfer portal matures and mid-major programs build deeper benches with high-level transfers, the talent gap that once made a 12-over-5 an upset will shrink further. The bracket categories won’t change. The reality inside them will.

Think about the last time your bracket survived the first weekend intact. If you can’t remember it, consider whether your bracket-building process is actually evolving or just repeating the same optimistic mistakes with different team names.

Your Next 3 Steps

1. Pull KenPom’s adjusted tempo data before your next bracket is due. Specifically, identify every 5-versus-12 and 6-versus-11 matchup where the lower seed plays 4 or more possessions per game faster. Flag those games as high-variance. Don’t auto-pick the favorite.

2. Add at least one 12-seed to your Sweet 16. Not randomly. Pick the 12-seed with the highest adjusted offensive efficiency ranking among all double-digit seeds in the field. Since 2015, at least one 12-seed has reached the Sweet 16 in 7 of 9 tournaments, per NCAA tournament records. Stop pretending it won’t happen again.

3. Track three-point attempt rate for your Final Four picks. According to Synergy Sports’ 2023-24 tracking data, teams that attempt fewer than 28% of their shots from three in the regular season underperform their seed expectations in tournament play at a 19% higher rate. If your Final Four pick is three-point-averse, understand the risk.

The 2018 UMBC win didn’t change the tournament. It revealed what the tournament had always been. A structure built for giants that occasionally, violently, eats them alive.

Marcus Tillman is already building his 2025 bracket. This time, he’s starting with the 12-seeds.