Sixteen observations on the NCAA tournament’s Sweet 16:

1. The bracket has been ransacked to a rare degree. The average remaining seed is 5.3, which is the fourth-highest in history and the highest since 2000, when it was also 5.3.

The last time a single region was destroyed the way the South is this year was 2011, when top-seeded Kansas was joined by No. 12 Richmond, No. 11 Virginia Commonwealth and No. 10 Florida State in San Antonio — an average seed of 8.5. This year the South’s foursome of No. 5 Kentucky, No. 9 Kansas State, No. 7 Nevada and No. 11 Loyola Chicago has an average seed of 8. But this was the first time one region has lost all its top four seeds before the Sweet 16.

One side of the bracket is particularly messy, with the following eight teams remaining: third-seeded Michigan, No. 4 Gonzaga, No. 5 Kentucky, No. 7 Texas A&M, No. 7 Nevada, No. 9 Florida State, No. 9 Kansas State and No. 11 Loyola. One of those teams will play for the national title on Monday, April 2, in San Antonio.

There are as many No. 11 seeds still playing (Loyola Chicago, Syracuse) as there are No. 1 seeds (Villanova, Kansas). And of course, for the first time ever, a No. 16 seed beat a No. 1 seed — we were all Retriever Believers for a weekend after UMBC shocked Virginia.

Throw in three buzzer-beating shots to win and a couple of stupefying comebacks, and yes, it has been sheer Madness. One of the wildest tournaments ever. Which was the general expectation after a tumultuous regular season.

2. Despite the chaos, the two conferences everyone believed were the best all season have the most teams still playing. The Big 12 has four teams advancing: Kansas, Kansas State, Texas Tech and West Virginia. The Atlantic Coast Conference also has four: Duke, Clemson, Florida State and Syracuse — with three of them clustered in one region. The Big Ten has two teams (Michigan and Purdue), as does the Southeastern Conference (Kentucky and Texas A&M). The Big East (Villanova), Mountain West (Nevada), West Coast (Gonzaga) and Missouri Valley (Loyola) have one apiece.

3. The biggest conference loser, by far, is the Pac-12. The league only got three bids, and those three teams (Arizona State, Arizona and UCLA) combined to go 0-3. The Wildcats’ ghastly blowout loss to Buffalo was the worst performance of the tourney — until Virginia-UMBC happened. Combine the Pac-12’s poor results in this tourney with the league’s lousy football season, and there are mounting competitiveness issues in the revenue sports on the West Coast.

4. After listening to John Calipari’s annual whine about his draw, the path to San Antonio has magically opened wide for his team. Kentucky has defeated teams seeded 12th (Davidson) and 13th (Buffalo) to reach Atlanta, where Big Blue fans will inhale every ticket to see the Wildcats play No. 9 seed Kansas State. If Kentucky wins that one, the regional final opponent will be either Loyola or Nevada. Kentucky will be heavily favored to win that region.

5. It was a brutal Sunday for the city of Cincinnati, which entered the day with two teams favored to advance to the Sweet 16 and left it with two stunningly blown leads and upset losses. First, Cincinnati threw away a 22-point lead in the second half against Nevada, being outscored 32-8 in the final 11 minutes. It was the second-largest comeback in NCAA tournament history.

Then Xavier, which led by 11 points with 8:30 to play, was outscored 25-9 the rest of the way. The Musketeers dissolved into a puddle of turnovers and missed shots, with star player Trevon Bluiett playing especially poorly in the final 10 minutes.

It’s hard to decide which of those end results was more shocking — a Cincinnati team with the No. 2 defense in the nation, according to Ken Pomeroy, being ripped for 32 points in 11 minutes, or a Xavier team that has the No. 8 offense scoring nine points in 8:30.

6. UMBC owned the first weekend of the tourney with its historic upset, but Loyola cornered the market on endgame drama. The Ramblers won both their games on last-second shots when staring defeat in the face: First it was a Donte Ingram 3-pointer to beat Miami 64-62, then it was a Clayton Custer jumper that danced around the rim before falling to beat Tennessee 63-62.

Loyola certainly tested the mettle of its most famous fan, 98-year-old Sister Jean, but she impressively withstood the assault on her nerves — and the media assault as well. She was asked Sunday about becoming a national sensation and responded, “Really, if I can correct you, international.”

She has become the breakout star of the tournament.

7. Four coaches are in their first Sweet 16: Brad Brownell of Clemson; Porter Moser of Loyola; Eric Musselman of Nevada; and Chris Beard of Texas Tech.

8. Nine remaining coaches have been to at least one Final Four: Mike Krzyzewski, Jim Boeheim, Bruce Weber, Bill Self, Bob Huggins, John Beilein, John Calipari, Jay Wright and Mark Few. Five of them have won national titles: Krzyzewski, Boeheim, Self, Calipari and Wright.

9. Two coaches with national titles and excellent NCAA tournament records turned in two of the biggest busts Sunday.

Tom Izzo’s No. 3 seed Michigan State utterly gagged against Boeheim’s 2-3 zone, scoring a mere 53 points while shooting 31 percent from two-point range and 22 percent from 3-point range. The Spartans were completely flummoxed by the zone, and Izzo’s refusal to put anyone with shooting ability in the middle of his zone offense was mystifying.

And then there was Roy Williams, whose defending national champion North Carolina team was blown out by seventh-seeded Texas A&M. The Tar Heels were bad defensively and launched a staggering 31 3-pointers, making just six.

10. Three Sweet 16 schools do not play FBS football: Villanova, Loyola and Gonzaga. Two of those (Loyola and Gonzaga) don’t play football at all. Loyola has just six varsity men’s sports.

11. Average margins of victory thus far in the tourney, largest to smallest: Villanova 24.5; Duke 23.5; Clemson 21; West Virginia 20; Purdue 14.5; Kentucky 12.5; Texas A&M 12.5; Kansas 10; Florida State 9; Kansas State 8.5; Michigan 7.5; Texas Tech 6.5; Gonzaga 5; Syracuse 3.7; Nevada 3; Loyola 1.5.

12. Half the teams left have at least nine losses on the season. Only four of them (Loyola, Nevada, Kansas and Gonzaga) won their league regular-season titles. Six won their league tournaments (Loyola, Kansas, Gonzaga, Michigan, Kentucky and Villanova). The regular-season champions of five of the Power Six leagues have all been eliminated: Virginia of the ACC, Xavier of the Big East, Michigan State of the Big Ten, Auburn/Tennessee of the SEC and Arizona of the Pac-12.

13. The old canard about defense winning championships isn’t holding up well in this tournament. Five of Ken Pomeroy’s top six offensive teams are still playing (Villanova, Purdue, Duke, Kansas and Nevada are in; Wichita State is out). Only three of his top six defensive teams have advanced (Virginia, Cincinnati and Tennessee are out, while Michigan, Texas Tech and Syracuse play on).

14. Worst performance of the second round goes to Auburn, which at one point trailed Clemson by 40 Sunday, before losing by 31. The dismissal of the Tigers means that every school mentioned in the U.S. Attorney’s federal complaint in the corruption probe of college basketball has been eliminated. Auburn joins Arizona, Miami and Alabama on the eliminated list, while Louisville, USC and Oklahoma State were snubbed by the NCAA selection committee.

15. Longest active winning streaks of the remaining teams: Gonzaga 16; Loyola 12; Michigan 11; Villanova 7.

16. After considerable damage to my bracket, updated picks to win each region: Kentucky in the South; Michigan in the West; Villanova in the East; Duke in the Midwest. Updated Final Four picks: Michigan over Kentucky and Villanova over Duke. The national title game remains the same: Villanova over Michigan.

More NCAA tournament coverage from Yahoo Sports:
• Nevada stuns Cincy with comeback better than Pats over Falcons
• Jim Boeheim uses controversial tactic to outcoach Tom Izzo and clinch upset
• Michigan player stops celebrating to console heartbroken opponent
• UMBC gets a special gift from Steph Curry before Kansas State game