[DC 86]

>20% of minutes basically means the team would have had to have at least two one-and-dones, because even the best players are not going to play every minute of every game.  I would be interested in knowing how many national champions had at least one one-and-done.

BC

In the one-and-done era (14 tournaments, 2006 - 2019) there have been four national champions that included at least one one-and-done on their roster:

2012: Kentucky had three (Teague, Davis, Kidd-Gilchrist) - accounted for 48% of total minutes.
2015: Duke had three (Jones, Okafor, Winslow) - accounted for 46% of total minutes.
2017: North Carolina (Bradley) - accounted for 7% of total minutes.
2018: Villanova (Spellman) - accounted for 14% of total minutes.

So there are two champions that relied very heavily on their one-and-dones, and two that received some contribution from a one-and-done.

The other ten national champions had no one-and-dones on the roster.

Reasonable point about the 20% threshold, so let's drop the threshold and just look at teams that had any one-and-dones on the roster, regardless of how many minutes they played:

4 of 14 national champions.
4 of 14 national runners-up.
5 of the remaining 28 final fours teams.
13 of the remaining 56 elite eight teams.
11 of the remaining 112 sweet sixteen teams.
17 of the remaining 224 round of thirty-two teams.
21 of the remaining 448 teams that played in the main tournament (i.e. not including losers in the play-in games).

21 teams with one-and-dones weren't selected for the NCAA tournament at all during this time.

In summary, of the 896 teams that participated in the round of 64, 75 (8%) included at least one one-and-done and 821 (92%) did not.

[DC 86]

>20% of minutes basically means the team would have had to have at least two one-and-dones, because even the best players are not going to play every minute of every game.  I would be interested in knowing how many national champions had at least one one-and-done.

BC

In the one-and-done era (14 tournaments, 2006 - 2019) there have been four national champions that included at least one one-and-done on their roster:

2012: Kentucky had three (Teague, Davis, Kidd-Gilchrist) - accounted for 48% of total minutes.
2015: Duke had three (Jones, Okafor, Winslow) - accounted for 46% of total minutes.
2017: North Carolina (Bradley) - accounted for 7% of total minutes.
2018: Villanova (Spellman) - accounted for 14% of total minutes.

So there are two champions that relied very heavily on their one-and-dones, and two that received some contribution from a one-and-done.

The other ten national champions had no one-and-dones on the roster.

Reasonable point about the 20% threshold, so let's drop the threshold and just look at teams that had any one-and-dones on the roster, regardless of how many minutes they played:

4 of 14 national champions.
4 of 14 national runners-up.
5 of the remaining 28 final fours teams.
13 of the remaining 56 elite eight teams.
11 of the remaining 112 sweet sixteen teams.
17 of the remaining 224 round of thirty-two teams.
21 of the remaining 448 teams that played in the main tournament (i.e. not including losers in the play-in games).

21 teams with one-and-dones weren't selected for the NCAA tournament at all during this time.

In summary, of the 896 teams that participated in the round of 64, 75 (8%) included at least one one-and-done and 821 (92%) did not.