Heading into Friday afternoon, the major topic of discussion surrounding the Michigan State Spartans was their status as a No. 2 seed who also happened to be one of the two top favorites to win the 2016 national championship.

Now, the 2015-16 Spartans will forever be remembered for something far less envious: Being on the receiving end of the biggest upset in the history of the NCAA Tournament. It's a statement that seems hyperbolic until you dig into the minutiae of just how improbable Middle Tennessee State's 90-81 triumph was.

A total of 13.02 million brackets were entered this year on ESPN.com, and 22.3 percent of them had Michigan State winning it all. The only team to receive more love from the American public was No. 1 overall seed Kansas, which got the top nod 25.0 percent of the time.

Those gambling with actual money were even more confident about Michigan State's March odds.

More money was bet on Michigan St to win NCAA tournament than any other team @LVSuperBook. #MarchMadness — David Payne Purdum (@DavidPurdum) March 18, 2016

This was a Spartan team that was the consensus No. 1 team in the country before potential national Player of the Year Denzel Valentine was sidelined with a knee injury in December, a three-week hiatus which likely cost Sparty a No. 1 seed in the Big Dance. Still, the overwhelming opinion was that even if its resume didn't reflect it, Tom Izzo's team was playing as well, if not better, than any other team in America heading into the tournament.

Michigan State is the first No. 2 seed that spent time at No. 1 in the AP poll to lose to a No. 15. cc: @laurakeeley @stevewisemanNC — Patrick Stevens (@D1scourse) March 18, 2016

The other part of this equation, of course, is Middle Tennessee State, a team which went 13-5 in Conference USA and lost non-conference tilts to the likes of Georgia State, Murray State and South Dakota State. According to Ken Pomeroy's ratings, the Blue Raiders entered Friday with the 198th-most efficient offense in Division-I. The 72.7 points per game they were averaging as a team ranked 189th in the country.

That same team, with those same credentials, led from start to finish and put up 90 points on not just any Tom Izzo team in March, but likely one of the two or three best Tom Izzo teams in March. They also did this on an afternoon when the Spartans buried 10 three-pointers and shot 56.0 percent from the field.

Every time it seemed as though MTSU was on the verge of folding in the manner teams in their position are supposed to, something borderline miraculous took place.

All five Blue Raider starters scored in double figures, led by junior Reggie Upshaw's 21 points. As a team, MTSU shot a blistering 55.9 percent from the field, and connected on 11 of its 19 3-point attempts.

Two seeds have lost in the first round before, but never like this. Never when the consensus was that the team being upset didn't just have a shot to win it all, but was arguably the favorite to win it all.

Middle Tennessee State now moves on to face Syracuse on Sunday, and that's fine, but win or lose, their spot in March Madness lore has already been solidified. No one has ever pulled a more stunning upset.

WATCH: Tom Izzo's emotional post-game press conference