Washington snapped BYU's 16-game winning streak. The Cougars, who started five freshmen against Washington and six against Northwestern, finished 34-23.
"We had a great year," BYU coach Gordon Eakin said. "They [his players] deserve credit for as far as we came."
Northwestern (35-17) plays Washington (35-13) for the regional championship today at 1 p.m. MT at Husky Softball Stadium. The Huskies are the only team yet to lose at the regional, so Northwestern would have to beat Washington twice today to advance to the Super Regionals next week.
The Wildcats, one of the nation's top offensive teams, pounded 14 hits off BYU pitchers McKenna Bull and Tori Almond. Three of the hits left the yard.
"We never recovered from the Washington game," Eakin said. "Washington took it to us.
"Northwestern's a great team, but we just didn't rebound. We didn't play anywhere near as well as we're capable of playing."
Almond and Bull combined on a four-hitter in Thursday's opening round, when the Cougars downed the hard-hitting Wildcats 7-2. Both pitchers were battered in the rematch.
"I guess yesterday was so emotional," Eakin said. "They just didn't have it today."
Northwestern freshman Nicole Bond gave up three runs and four walks in the first inning, then was yanked after walking No. 9 hitter Ashlee Robinson to start the second inning. Senior Sammy Albanese (6-6) scattered six hits over the final six innings, and she belted a pinch-hit, two-run homer in the fourth.
"Sammy was awesome," Northwestern right fielder Andrea DiPrima said. "We love it when Sammy's out there. She's a competitor. She's fierce."
The Huskies, seeded 12th in the 64-team NCAA tournament, outhit the Cougars 9-2. Hot-hitting left fielder Whitney Jones bashed a three-run homer to right-center in the first inning, then launched a two-run shot to center in the fourth inning, a ball that left the entire stadium.
Almond (11-7) lasted just two-thirds of an inning against Washington, giving up four runs on five hits. Bull pitched the remaining 4 1-3 innings and threw 103 pitches.
Washington senior Bryana Walker, mixing pitches expertly, gave up two hits and struck out five. She improved her career record in NCAA tournament games to 7-1.
"She's as good as it comes," Eakin said. "She has all the pitches."
"We weren't ourselves," BYU first baseman Katie Manuma said. "We weren't aggressive, so we made her better than she is."
The Huskies have outscored rivals 44-4 during a five-game winning streak. Their last three games have ended early due to the eight-run rule.
• BYU's season came to an end when Northwestern pounded 14 hits, including three homers.
• BYU freshman catcher Sydney Broderick lost a 16-game hitting streak and a 26-game on-base streak at the tournament before going 2-for-3 with two doubles against Northwestern.
• Washington started seven batters hitting above .325.