The No. 2 seeds are Michigan State (28-6), Tennessee (29-5), Kentucky (27-6) and Michigan (28-6). The first of these edged the last of these in the Big Ten conference final minutes before the bracket was released. Yet it was the defeated Wolverines who received the privilege of placement in the West alongside Gonzaga, while the Spartans — who won all three games against their in-state rival this season — landed in Duke’s dreaded quadrant.

The Blue Devils finished the regular season on a 3-3 skid without Williamson, who sprained his knee when his shoe ripped open during a game on Feb. 20. But Williamson, the prospective No. 1 overall pick in the N.B.A. draft, returned last week, and Duke proceeded to stomp through the A.C.C. tournament. Williamson set the Duke scoring record for that event, with 81 points.

The selection committee effectively ignored the non-Williamson .500 squad and instead considered the team that has won every game except for a 2-point loss to Gonzaga and an overtime loss to Syracuse (20-13). It is Duke’s first No. 1 seed since 2015, which is also the last year it won the tournament.

“They earned their right to be there,” said the selection committee chairman, Bernard Muir, who is Stanford’s athletic director, when he appeared on CBS’s selection show to discuss the bracket.

The most challenging of the four regions appeared to be the South, topped by Virginia. If the Cavaliers get past 16-seeded Gardner-Webb (23-11) on Friday — a game they surely will not take for granted after last year — they could face a No. 8-seeded Mississippi (20-12) that has four wins over tournament teams. Then potential round of 16 opponents include Wisconsin (23-10), underseeded at No. 5, or fourth-seeded Kansas State (25-8), which came close to the Final Four last year.