OKLAHOMA CITY -- A two-run home run for Lauren Chamberlain in the bottom of the fourth inning ripped open a tight game as Oklahoma opened the 2012 Women’s College World Series with a 5-1 victory against South Florida.

The Sooners (51-8) advance in the winners bracket to face the Cal/LSU winner at 7 p.m. ET Friday . The Bulls (50-13) will return to the field at noon Saturday against the Cal/LSU losing team in an elimination contest.

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Oklahoma 5, South Florida 1
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The game started as a pitchers duel, and was dominated by pitching for the first three innings. USF’s Jessica Mouse ripped a one-out double to left center for USF in the top of the first, but was unable to advance.

That would be the only hit for either team until the top of the fourth. In that inning, Mouse lead off for the Bulls and reach the bases on a fielding error. After Mouse advanced to second base on a groundout, USF head coach Ken Eriksen pinch-ran for Mouse with Courtney Goff, who scored on a single through the right side by Kourtney Salvarola to give the Bulls a 1-0 lead.

The Bulls’ lead would be short-lived, as Oklahoma got its first hit of the game to lead off the bottom of the fourth when Destinee Martinez roped a ground ball single through the left side. She would advance to second base on an illegal pitch before Lauren Chamberlain followed with a home run roped over the centerfield fence, her 28th of the season, to give the Sooners a 2-1 lead. Catcher Jessica Shults drew a one-out walk and advanced to second before pinch-runner Ali Vandever was thrown out stealing third base to end the inning.

USF pitcher Sara Nevins was removed in the top of the fifth inning after issuing a one-out walk to designated player Katie Norris. Her replacement in the circle, Lindsey Richardson, finished strong with two strikeouts to end the inning before Norris returned to the circle for the bottom of the sixth.

Chamberlain added a one-out double in the bottom of the sixth inning to finish her day 2-for-3 with two runs scored and two RBI. Ricketts followed with a triple off the left field wall to score Chamberlain and extend OU’s lead to 3-1. Ricketts’ shot missed a home run by inches, bouncing just below the yellow home-run line on the outfield wall.

USF used three pitchers in the bottom of the sixth inning, but all three struggled with the Sooners bats. A Brianna Turang single and a bases-loaded walk to Brittany Williams brought the score to a 5-1 Oklahoma. Ricketts closed out the top of the seventh for her 38th win of the season, finishing with 11 strikeouts on the day. The lone run she allowed on the day was unearned.

The fourth-inning home run from Oklahoma freshman Lauren Chamberlain was her 28th of the year. That extends her lead atop OU’s single-season all-time list and places her ninth on the NCAA’s all-time single-season list for Division I softball. Arizona’s Laura Espinoza holds the all-time record with 37 home runs in 1995.

Entering Thursday’s game, USF was 42-2 when scoring first. The Bulls plated the first run of Thursday's game, an unearned run in the top of the fourth inning, but gave up five unanswered runs in the loss.

OU’s win ended a four-game WCWS losing streak that dates back to 2004. That season, Oklahoma defeated Washington 6-2 in the opening game for both teams.