The Ducks opened their scoring in the fifth, starting with a single from Alexis Mack, followed by a pair of walks to Svekis and Udria loaded the bases with one out.
Still, with no outs, a two-run single by Udria cut the United Kingdom lead to 5-4.
Mercado got caught between third base and home plate for the second out, and Rhodes grounded out to stand two base runners in the top of the first inning.
Mia Camuso delivered the go-ahead knock the Ducks were looking for all afternoon.
The Ducks then achieved two straight groundout RBI as the OR batters only had to put the ball in play for their teammates to score. Gwen Svekis then walked to load the bases.
The other featured star of the United Kingdom defense, All-SEC First Team shortstop Katie Reed, committed a rare error for the second straight game in this NCAA tournament. Alex Martens followed with an RBI double to left-center. She began the game-wrecking sixth inning by walking two batters and hitting another, loading the bases before the ball was ever put in play.
A ground out to third baseman Jenna Lilley ended the game and started an on field celebration, including hats that read "OKC bound".More news: Drake Meets Celine Dion Backstage at the 2017 Billboard Music Awards
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Abby Cheek's solo home run in the fourth inning gave Kentucky (39-19) a 3-0 lead, but OR answered with two runs in the fifth inning to narrow it. Erin Rethlake hit a two-run double in the bottom of the sixth to extend the Wildcats' lead.
OR got on the board in the top of the fifth inning on an illegal pitch and an RBI groundout.
Kentucky, the home team in the second game of the best-of-three series, got on the board first Saturday with two runs in the bottom of the first inning.
Meagan Prince struggled mightily in the rematch against the third-seeded Ducks, as she only notched two strikeouts and gave up all four runs for the Cats.
Udria hit into a double play to strand two bases runners in the third.
Miranda Elish (11-0) pitched the final three innings in relief of Maggie Balint.
Instead, the Ducks will look to bring home the first national championship in program history. "We have to be in the moment and never take one pitch off, because it could be our last".