Giant Killers' 10 most likely first-round upsets in March Madness bracket 2021

Gonzaga unveiled as NCAA tournament's No. 1 overall seed (1:05)

Jay Bilas, Seth Greenberg and LaPhonso Ellis break down how good Gonzaga is as the Bulldogs are revealed to be the NCAA tournament's No. 1 overall seed. (1:05)

It's upset-picking time.

Whether you've been glued to conference play or just found out that there's an NCAA tournament this year, we're all searching for that 12-over-5 upset that's going to hit. And if you're anything like us, you want some numbers to point you in the right direction.

Giant Killers is here to help. Back for its 15th NCAA tournament, Giant Killers is our metric-based model that predicts the likelihood of upsets. You can read the details here, but the idea is fairly straightforward: Giant Killers takes the base probability of an upset from ESPN's College Basketball Power Index but adds a further wrinkle of incorporating the strengths, weaknesses and style of the two teams in each individual matchup.

As always, Giant Killers exclusively considers matchups with at least a 5-line seed differential (so, a No. 11 over a No. 6 in the first round, for example).

There are no sure things in the NCAA tournament, other than that there will be upsets -- and our model is here to try to identify them before they happen. Here are Giant Killers' top 10 most likely upsets of the first round.