Arizona was still close despite a not-so-crisp first half.
Once California switched to a zone to start the second half, the Wildcats didn't know what to do and became the latest top-10 team to go down.
Indecisive and tentative against Cal's zone, No. 7 Arizona fell into a 10-point hole in the second half and never fully recovered, losing 77-69 Sunday night to become the sixth top-10 team to fall this week.
"We took ill-advised shots," Arizona coach Sean Miller said. "It looked as if we had no idea what we were during for that brief three-minute period."
Cal (14-9, 6-5 Pac-12) rallied from a 15-point deficit behind its defense against Arizona State on Thursday before coming up just short in a 66-62 loss.
The Bears went to their zone earlier against Arizona, keying a 17-2 run that put them up 10.
Even as the Wildcats started to figure out the zone, Cal didn't flinch, making some big shots down the stretch to beat Arizona at the McKale Center for the third straight season.
Allen Crabbe scored on a tough shot along the baseline with just over 2 minutes left and had 19 of his 31 points in the second half. Justin Cobbs hit a keep-em-at-bay 3-pointer just before that and scored on a layup with 39 seconds left, finishing with 21 points.
"We had a rhythm and communication," Cal coach Mike Montgomery said. "They had some penetration, but it took them out of their norm. We haven't been very good at it this season and it was a matter of game and circumstance."
Arizona (20-3, 8-3) had a rare letdown on defense, allowing Cal to shoot 59 percent. Mark Lyons scored 16 points, Solomon Hill added 13 and Brandon Ashley 12.
The Wildcats had won five in a row before joining Indiana, Florida, Michigan, Kansas and Ohio State as top-10 teams to take a tumble this week.
"We let the zone affect us and didn't get the ball movement we needed," Hill said. "When you don't get things rolling on the offensive end, it takes you mentally away from the game."
Arizona has had a penchant for getting off to slow starts this season, particularly at home, of all places.
The Wildcats did it against Florida in a matchup of top-10 teams in December before rallying for a victory and did the same thing against Stanford on Wednesday, almost spoiling the 40th anniversary of the McKale Center opening doors.
Arizona wasn't so fortunate against UCLA on Jan. 24, unable to bounce back after missing 12 of its first 13 shots and falling behind 19-3.
The Wildcats weren't as bad as they were against UCLA, but weren't particularly sharp, either.
Arizona struggled with its shooting early and had some breakdowns defensively, allowing Cal to make 15 of 28 shots and Crabbe to score 12 points on 6-of-8 shooting.
The Wildcats still managed to lead 38-33 at halftime, thanks to Hill's 11 points and 10-of-13 shooting from the free-throw line.
The Bears helped Arizona out with eight mostly careless turnovers — two by David Kravish sailed directly into the crowd — that led to 12 points for the Wildcats.
Once the second half started, Cal tried to run away with it.
The Bears gave Arizona State problems by switching defenses with 8 minutes left in Thursday's game. Cal got its defensive mojo going earlier against Arizona by switching to a zone to start the second half.
The Wildcats struggled to decipher the zone and opened the half by missing nine of their first 10 shots, many of those late in the shot clock and contested.
At the other end, the Bears made their first five shots to open with a 17-2 run, going up 50-40 on Crabbe's four-point play.
"We haven't seen a zone in a while, so it threw us off," Arizona swingman Kevin Parrom said.
The Wildcats clawed their way back with a 9-2 run to stay within reach, but never made it all the way back.
Arizona pulled within two on a 3-pointer by Lyons with 2:02 left, but Crabbe answered with a tough baseline drive and Cobbs followed with his layup that made it 75-69, sending the Bears to their biggest road win of the season.