One game by itself can be misleading, but net efficiency margin (NEM) at least gives us a way to compare each team's performance from the same baseline. So who had the best games over the first two (real) days of the tournament?

All raw efficiency data is from the sublime I used the ratings through last Sunday's games to make the comparisons. (For my second round reviews, I'll update the ratings through the end of the first round, and so on.)

Top overall performances

2.GonzagaWest Virginia52.7
4.GeorgetownBelmont45.4This partly due to Belmont's overrating by Pomeroy's rating system, but nonetheless a solid performance.
5.South FloridaTemple40.6Didn't see that coming.

Top offensive performances

1.Norfolk StateMissouri37.5Mizzou isn't known for their D, but this was the best offensive showing against the Tigers all season.
3.GonzagaWest Virginia30.7The Zags also had the third best offensive NEM in the round of 64 last year.
4.Iowa StateUConn29.1Not a bad showing. We'll see whether they can keep it up against Kentucky.
5.MissouriNorfolk State29.1Perfect exemplar of Missouri's season.

Top defensive performances (lower scores are better)

1.Murray StateColorado State-45.5When a tournament-worthy team scores 0.66 points/possession, it's a mix of good defense and putrid offense.
2.South FloridaTemple-36.6Defense has carried the Bulls all season.
4.KansasDetroit-32.6Seeing two #2 seeds go down earlier in the day certainly helped Bill Self get his players' attention.
5.St. LouisMemphis-28.9