No. 18 Arizona 79, Colorado 69: Nick Johnson scored 18 points as the Wildcats held off a late charge by the Buffaloes in the quarterfinals of the Pac-12 tournament in Las Vegas.

Fourth-seeded Arizona (25-6) overcame a poor shooting game by leading scorer Mark Lyons and advanced to Friday’s semifinals matchup against top-seeded UCLA, which defeated the Wildcats in both of their regular-season meetings.

Spencer Dinwiddie scored 18 points to lead fifth-seeded Colorado (21-11), which trailed by 14 with 12:29 left before cutting the deficit to 71-67 on Askia Booker’s 3-pointer with 1:56 to play.

Andre Roberson, who finished with 15 points and 11 rebounds, made two free throws with 1:03 left to cut the lead to 71-69 before Arizona closed the game with eight unanswered points. Booker chipped in 12 points on 4-of-10 shooting for the Buffaloes.

Lyons scored 14 points on 4-of-13 shooting and missed seven of his nine shots from beyond the arc, but he made a key 3-pointer with 2:06 left to put the Wildcats ahead 71-64. Solomon Hill added 13 points and seven rebounds for Arizona, which won two of its three games against the Buffaloes.

GAME NOTEBOOK: Arizona improved to 11-4 in the Pac-12 tournament since 2002 when scoring at least 70 points. … Lyons is shooting 25.5 percent (12-of-47) over his last four games. …Colorado allowed an opponent to score more than 70 points for the first time in its last 12 games.