Mills, who set a school record for points by a freshman, also dished out five assists. Diamon Simpson scored 18 points to go along with 12 rebounds for Saint Mary's (4-0), and Omar Samhan added 16 points. Todd Golden chipped in nine points and eight boards.
The Gaels, 4-0 for the first time since 1993-94 when they were 5-0 to open the season, made 13 of 15 free throws down the stretch.
Kamyron Brown scored a team-high 20 points for the Ducks (4-1), who are tied with Michigan State for No. 11 in the USA Today/ESPN coaches poll. Maarty Leunen posted a double-double with 17 points and 11 rebounds. Tajuan Porter supplied 13 points and Malik Hairston had 12 points. Joevan Catron and LeKendric Longmire each donated 11 points in the loss.
Yusef Smith's layup gave the Gaels a 12-point lead, 68-56, with 11:48 remaining in the second half.