A slow start inside led to struggles on the outside for Arizona in a surprising home loss.
The sixth-ranked Wildcats try to regroup and avoid an empty weekend at home in Pac-12 play when they face Southern California on Saturday night.
Arizona (16-2, 4-2) missed 12 of its first 13 shots - many from close range - against UCLA on Thursday and fell behind 21-5. While the Wildcats pulled to within four points in the second half, they never put themselves in a position to tie or take the lead in an 84-73 defeat, dropping two games behind front-running Oregon in conference play.
Coach Sean Miller thought his team's early struggles exposed his team's youth, with his players trying to do too much individually to start the comeback.
"Even though our guys fought hard, we weren't playing team basketball or executing," Miller said. "We ended the game with 10 assists, but that's not good enough in a game like this.
"We missed maybe five or six, what I would call really good shots, early in the game. When you're down 21-5 at home it's not a good feeling. Some of the plays we made were a function of us trying to make big plays."
Arizona never found its rhythm on the perimeter, shooting a season-low 20.8 percent (5 for 24) from 3-point range - well off its Pac 12-leading season mark of 37.1. Starting guards Mark Lyons and Nick Johnson totaled 39 points but went a combined 3 for 12 from beyond the arc.
"We missed easy shots," said Johnson, who finished with 23 points. "I wouldn't say it's something we did wrong in practice or our execution, our shots just wouldn't fall."
Lyons leads the team with 15.2 points per game and 33 3-pointers made, but the senior transfer from Xavier was 2 for 7 from 3-point range Thursday. He's made four of 17 from behind the arc his last three games.
Those shots, though, could fall against USC (8-12, 3-4), which is last in the Pac-12 defending the 3-pointer at 36.8 percent. The Trojans made a season-high 15 3s but allowed Arizona State to make nine in a 98-93 overtime road loss Thursday, falling to 1-2 under interim coach Bob Cantu.
"It was great because we've been trying to pick up our offense, but in doing so, we have to tighten up our defense," Cantu said. "If we don't, we can't expect to win on the road."
J.T. Terrell has played well since Cantu replaced Kevin O'Neill, averaging 18.3 points while making 11 of 26 from 3-point range to improve his season mark to 10.6 points per game. The junior guard had averaged 6.0 points and shot 28.8 percent in his previous eight games.
Jio Fontan scored a season-high 25 points while Nic Wise matched a season best with 19 and added 10 rebounds against the Sun Devils. The Trojans are shooting 35.2 percent from 3-point range overall but 41.2 percent in their six road contests.
USC has lost all four games against ranked opponents this season, but only once by double digits. The Trojans have dropped six straight to Top 25 teams since a 65-57 win over then-No. 10 Arizona on Feb. 24, 2011, and four in a row at the McKale Center since a 70-58 victory Feb. 28, 2008.