TULSA, Okla — And then there were sixteen.

After a whirlwind first four days of the 2019 NCAA Tournament, the field has been halved with each of the first two rounds, and left standing are only the teams fortunate enough to have won twice. The Sweet 16.

We've seen a little of everything over the frenzied first few days. Ja Morant's rise to superstardom and subsequent exit out of the NCAA Tournament came in a flash. LSU gave us our first (and thus far) only buzzer-beater. UCF, meanwhile, almost gave us a buzzer-beater against Duke. 

So yes, a lot has gone down. 

If you missed a beat from the day that was, we've got you covered. 

1. North Carolina is peaking at the right time

What's that, you say? A North Carolina team that features three potential first-round draft picks and is coached by a Hall of Famer is taking shape at just the right time? Seems like an average March for the Tar Heels.

UNC made short work of No. 9 seed Washington, a team that cruised to the Pac-12 regular season title, on Sunday in an 81-59 beatdown. Impressive. Dominant. All the adjectives. But the way in which they did it brings up another descriptive term: jarring. 

North Carolina has been dominant this season riding veterans Cameron Johnson and Luke Maye with a heavy dosage of freshman Coby White sprinkled in down the stretch, but Sunday it was Nassir Little, the projected top-10 pick who's been a bit of an enigma, who saw his star brighten. Little scored 20 -- tied for a team-high with Luke Maye -- and exerted his will on Washington on both ends of the floor, using his length and athleticism to add 7 rebounds and a block. 

This was the Nassir Little UNC thought it was getting this season. He's peaking at just the right time, and so too are the Tar Heels, which advance to the Sweet 16 to face No. 5 seed Auburn in the Midwest Regional. 

2. Tennessee is officially living on borrowed time

No. 2 seed Tennessee got up by 25 points on Iowa in the first half of Sunday's game. 

The game wound up going to overtime.

Iowa returned from the dead to force an extra period, and while the Vols would go on to win 83-77, they've got to be thanking their lucky stars for being able to do so. They were hapless down the stretch in regulation and nearly came all the way apart at the seams before Grant Williams took over late without co-star Admiral Schofield who was in foul trouble. Coach Rick Barnes says Schofield actually chose to remain on the bench. "He kept saying leave Kyle [Alexander]  in the game." Barnes said after the win. "With four fouls, he knew they would come right at him. He said, Coach, I can't guard the way I can guard. I'm going to foul."

This should be a wake up call for a Tennessee team that should have cruised. The Vols were a clutch Iowa bucket away from from being eliminated, but instead, they are marching on, and on borrowed time. After surviving a near collapse, which would have tied for the biggest blown lead in NCAA Tournament history, Rocky Top might be feeling like it's got a wealth of house money on its side. 

3. Duke escaped doom

How's this for an escape job? Two shots at the rim to win it for UCF, both inches away from dropping and ending Duke's season, both rimming out. 

This was one of several instances where UCF could have put Duke away.

It takes a lot of talent, some great coaching, and some luck along the way to win a national championship. Duke checked all three boxes off on Sunday. 

UCF and Duke traded 13 leads in their second round clash, but in the end, Zion Williamson's 32 points and 11 rebounds coupled with RJ Barrett's 16 points (none bigger than the one below) proved too much for the Knights. So did the extra bit of luck. Duke is Sweet 16-bound. 

4. Texas Tech is devastatingly good

In a loaded West Regional that features No. 1 seed Gonzaga and surging No. 2 seed Michigan, Texas Tech might be the most equipped to advance of the bunch. The Red Raiders are devastating, their defense suffocating, and their offense ... lethal.

They crushed 32-win Buffalo on Sunday, and second half was not particularly close. 

Texas Tech allows only 59 points per game, the third-best in Division I. So for its defense to clamp down in a tournament game is none too surprising. But for its defense to hold Buffalo, a team that averaged more than 85 points per game this season ahead of Sunday, to only 58 points is startling. 

5. Virginia Tech at full strength could be a problem for Duke

Yes, it was without Zion Williamson, but Virginia Tech is one of only three teams to have defeated Duke this season. And guess what: Virginia Tech had an excuse against Duke at the time the two met, as Hokies' playmaker and third-leading scorer Justin Robinson was out. 

Now the two are at full strength. 

Williamson is back and seemingly better than ever, and Robinson is back, too, and rounding into shape after scoring 13 points and adding four assists in a 67-58 second round win over No. 12 seed Liberty.

Virginia Tech is a different team with a different defensive dynamic when Robinson is on the court. He's a hound on the perimeter defensively, a trustworthy general who initiates things on offense, and a savvy veteran whose been hard at it for four seasons. 

We're about to find out just how good Virginia Tech is at full strength with the most stacked talent in the NCAA Tournament, and whether the Hokies are capable of pitting their full strength roster up against Duke's for a shot at the Elite Eight. 

6. Virginia 2019 is better built than Virginia 2018

The metrics say it. The eye test prove it: Virginia is a better constructed team in 2019 than it was in 2018, when it fell in the first round as a No. 1 seed to No. 16 seed UMBC. 

It's fair to still be concerned about the Cavaliers and how their style of play projects in the postseason; they run a plodding offense and aren't built for coming back if they fall behind, but this team might just be good enough for that not to matter.

The major difference between 2019 and 2018, of course, is the presence of projected lottery pick Deandre Hunter. He sustained a shoulder injury and did not play in the tournament last year. And perhaps it is that simple, but after two consecutive defensive showings in which they absolutely suffocated their opponent, the latest victim No. 9 seed Oklahoma in a 63-51 snoozer, UVA fans can be optimistic that this year might be different than the previous early exits that have taken place under Tony Bennett. 

7. Houston can win any way it needs

If you want to run up and down the court and have a shootout, Houston will happily do so. If you want to muck the game up, make the Cougars run halfcourt sets and slow the pace to a crawl, Houston, it appears, will also happily do that, too.

Kelvin Sampson's club won 74-59 on Sunday to advance to the Sweet 16 using the latter style. Ohio State slowed the game to a crawl and forced both teams to execute in the halfcourt, and execute in the halfcourt Houston did. The third-seeded Cougars shot 46 percent from the floor and from 26 percent three-point range, neither of which is particularly great. But the Cougars defense limiting the Buckeyes to just 39 percent from the floor and forcing 14 turnovers is supporting evidence that when the offense isn't firing on all cylinders, the defense can carry this team.

8. Pac-12 isn't dead yet

The Pac-12 has what the Big East, a conference that rated better overall this season, does not: a puncher's chance to still win the 2019 national championship.

Washington was eliminated Saturday by No. 1 seed North Carolina to drop the count from 2 to 1. But Oregon -- the Pac-12's automatic qualifier who would not have been in the field if not for a magical run in the league's postseason tournament -- is alive and well after smashing the Anteaters of UC Irvine 73-54. Up next: A Sweet 16 shot at No. 1 seed Virginia in the South Regional.