TUCSON, Ariz. (AP) -- With a 22-point lead early in the second half, the Arizona Wildcats (No. 16 ESPN/USA Today, No. 20 AP) went into cruise-control. And it cost them.

Shaquala Williams scored 18 of her 24 points in the second half as Oregon erased a huge deficit to upset Arizona 75-71 Saturday.

"Our kids willed themselves to win," Ducks coach Jody Runge said. "It's so hard to come back from that bif of a deficit, but our defense really stepped up in the second half."

Oregon (22-7, 13-4 Pac-10) trailed 55-33 in the opening moments of the second half.

The Ducks rallied back with Williams' 3-pointer putting her team ahead to stay at 68-67 with 4:09 remaining.

They held on from there as Brianne Meharry, Jamie Craighead and Williams all made free throws in the final 2:02.

"This is the best win for us this season," Williams said. "Arizona came out blazing. They shot 60 percent. But we knew if we could just weather the storm, we'd be OK.

"We made our comeback with great transition offense. I could see it in their eyes that they lost their confidence."

The Wildcats (22-6, 11-5) had a couple of attempts to tie the game in the final 10 seconds. But an errant 3-point try by Reshea Bristol and then a turnover with 1.9 seconds ruined any comeback hopes.

"We can't worry about the tournament now. We have to worry about Stanford and Cal," said Arizona coach Joan Bonvicini, noting her team's final two regular-season games this week, both on the road. "We will find out what we are made of."

Courtney Moore finished with 17 points off the bench for Oregon and Craighead added 11.

Tatum Brown and Lisa Griffith scored 12 points apiece while Angela Lackey and Bristol each had 11 for Arizona, which blew a 36-29 halftime lead.

The game was played before a crowd of 5,272 at McKale Center, the largest ever to watch the Wildcats women.