SEATTLE -- BYU pitcher Paige Affleck allowed one hit in the final six innings against No. 21 Auburn and Caschjen Atagi scored both Cougar runs as BYU defeated the Tigers 2-1 on Thursday in the NCAA Regional.

Affleck finished with nine strikeouts and allowed just one walk in stifling Auburn and winning her 25th game of the year.

Atagi, who joined the team late last night after attending a family wedding, went 2-for-2 with two runs scored and a walk.

Atagi's double and ensuing steal of third base in the top of the second set up BYU's first run of the game after the Cougars fell behind 1-0 in the first inning. Atagi tied the game on a single to left field by Jessica Dugas.

After giving up a run on three hits and a wild pitch in the bottom of the first, Affleck settled in for the remainder of the contest to shut down the Tiger bats. The Mountain West Conference Pitcher of the Year allowed only two runners to reach base between the second and seventh innings to maintain BYU's one-run lead.

BYU scored what would be the game-winning run in the top of the fourth. A lead-off single by Atagi turned into two additional bases when the Auburn center fielder misplayed the hit, allowing Atagi to reach third.

BYU right fielder Delaney Willard brought Atagi home during the next Cougar at bat, hitting a sacrifice fly to right field that allowed Atagi to score.

With the win, BYU goes to the winner's bracket and will play the winner of No. 14 Washington and Portland State at 3 p.m. PT on Friday.