R.J. Barrett scored 20 points, Cam Reddish added 16 and top-ranked Duke remained undefeated at the Maui Invitational with a 90-64 rout over San Diego State.

The Blue Devils (4-0) shot 52 percent, made 10 of 25 from 3-point range and improved to 16-0 in Maui while earning a spot in Tuesday's semifinals against No. 8 Auburn.

Duke has been the talk of college basketball since its highly-touted freshmen shot the season out of a canon with a blowout win over then-No. 2 Kentucky. The five-time Maui champion Blue Devils arrived in paradise the favorites and played like it against the Aztecs (2-1).

Despite front-court foul trouble in the first half -- Zion Williamson played seven minutes -- Duke took control with an 11-0 run and led 49-32 by halftime behind Barrett's 16 points.

The Blue Devils kept the runaway going with an early 8-0 run in the second half, building the lead to 71-46 on Williamson's breakaway windmill dunk. Williamson had 13 points in 18 minutes.

Devin Watson had 15 points to lead San Diego State (2-1).