Grant is not even close to better at defense than Buchanan. Whatever that stat your pointing to is assessing it has to be flawed. Grant is the worst defender on the team at his position who sees meaningful minutes.
This is the breakdown of individual KenPom/Torvik Efficiency player vs player called BPR(Bayesian Performance Rating)
Player OBPR / DBPR
Francis +3.62 / -0.10 +3.52
Davis +1.05 / +1.05 +2.10
Grant +1.21 / +0.42 +1.63
Buch +0.94 / -0.63 +0.31
A lot of the defense stuff is because Davis 3rd yr and Grant 2nd to Francis and Buchanan 1st year here and understanding the defense better.
These are the stats why I can't see them keep 2 6'1 scoring PGs and Buchanan Wing/G to Grant Wing/F. They all need 25-30+ minutes in 26-27 but can't really play together on the same floor for long stretches. Decisions need to be made.
Francis 28-49 57.1%, 68-147 46.3%(49.0%), 3pt 34-102 33.3%
Davis 12-34 35.3%, 23-69 38.3%(37.2%), 3pt 22-62 35.5%
Davis shoots the 3 a bit better w/ defense or keep Francis just does things much better at a higher volume and hope the defense improves.
Grant 49-94 52.1%, 17-41 41.5%(48.9%), 3pt 19-57 33.3% 10.6pts/4.5reb
Buchanan 32-59 54.2%, 30-68 44.1%(48.8%), 3pt 10-25 40% 8.3pts/3.3reb
This team has many weaknesses and holes, we can't keep 2 guys filling the same role twice over, all upperclassmen 3 seniors and a junior. It won't work next year.
Powers combo guard different role, Zrno 3 PT specialist different role, Dortch 4/undersized 5(2.5pts, 3.5rebs), top defender on the team(DBPR +1.87, Davis 2nd +1.05) different role.
Top needs are Big and a scoring/rebounding forward or hope Dortch develops into a monster at the 4. Francis is worth 2nd/3rd on the team money.