Arizona (53-15) dropped into the loser's bracket and faces the winner of a Southern Mississippi-DePaul matchup in the Cats' next game at 6 p.m. Saturday. UW will face UCLA at 12 noon on Sunday.
Spediacci gave up a double to Lauren Bauer in the first inning then retired 17 consecutive batters before she allowed Nicole Giordano to reach base on her own throwing error in the sixth. She struck out seven.
The Huskies' tied a series record with four doubles. Their first four hitters in the lineup hit one apiece and three of them were involved in the scoring.
A walk by Shannon Walsh and back-to-back doubles by Rosie Leutzinger and Kelly Hauxhurst staked Washington to a 2-0 lead in the top of the third. Hauxhurst drove in both runs with a drive over Bauer's head.
The Huskies chased UA starter Jennie Finch (24-8) in the fourth. Becky Newbry led off with a double and and out later Mo Downs singled her in to push the lead to 3-0, and UA brought on Becky Lemke in relief. Lemke got a fly ball and a strikeout to end the inning.
Lemke allowed one hit in three and two-thirds innings, and struck out five.
Spediacci had shut the Cats out April 10 in Seattle when the Huskies beat UA 9-0 in a mercy-rule six-inning game during Pac-10 play. UA had beaten her May 8 in Tucson 3-0.
Arizona threatened in only one inning -- the first -- when Bauer's double extended her World Series hitting streak to five games. But Spediacci struck out Toni Mascarenas and Jennie Finch to end the inning.
The game might have been more one-sided had Bauer not reached over the left field fence in the top of the second to rob Mo Downs of a home run.
Arizona had beaten Washington in four of five games this season. It was the Cats' first loss to a Pac-10 team other than UCLA in 16 games against league opponents in 12 trips to the College World Series.