Five-star Duke signee
Cam Williams led St. Mary's with 23 points. Riordan added 14 while sophomore
Carter Bagley also contributed 11
points and knocked down three 3-pointers in the win.
See highlights from the Arizona semifinal in the video via the NFHS Network.
St. Mary's built a 9-2 lead to begin the game and led 39-31 at the half but Millennium clawed back to take a 55-49 advantage into the fourth quarter.

Mick Riordan is the grandson of Mike Riordan, who was a member of the 1970 New York Knicks championship team. (FILE PHOTO: Lonnie Webb)
A 7-0 spurt in the fourth quarter put St.
Mary's in position to pull the upset.
Williams
started the scoring with a 3-pointer before senior guard
Brody Postorino made a difficult
layup high off the glass on the next possession. Riordan added to the run with a fadeaway in the mid-range.
Top five sophomore prospect
Adan Diggs halted the run on the other end with a tough, contested 3-pointer as the shot clock was winding down. Diggs scored the final seven points of the game for Millennium as he connected on a pair of free throws and a tough mid-range shot from the right wing to give the Tigers a four-point advantage twice in the final two minutes.
However, it wasn't enough as Williams knocked down a clutch 3-pointer from the left corner to cut the margin to 64-63 before a double-team forced Diggs to pass up a go-ahead attempt on the other end that resulted in a miss from his teammate.
Following a timeout from St. Mary's with approximately eight seconds on the clock, a kicked ball followed by Millennium's final foul to give gave St. Mary's the ball on a sideline out-of-bounds in the half-court to set up the final shot. The Tigers chose to double-team Williams, which led to the open 3-pointer from Riordan.
Diggs scored a game-high 33 points in loss.