Oklahoma counters with a formidable offense led by a pair of sophomores, Ella Parker and Kasidi Pickering, who are hitting above .400. Oklahoma is second nationally with 115 home runs and fifth with 7.75 runs per game.
"We know we have an incredible opponent on Thursday, and we just want to put our best foot forward out here," Tennessee coach Karen Weekly said.
Adding to the difficulty of Oklahoma's mission, all four teams on its side of the bracket are from the SEC -- Oklahoma, Tennessee, Texas and Florida.
In other opening-day matchups, No. 12 seed Texas Tech will face unseeded Mississippi and No. 9 seed UCLA meets No. 16 seed Oregon in the nightcap.
The first part of the event is double-elimination. The final two teams will play for the title in a best-of-three series starting June 4.
Gasso wasn't sure her team would have a chance to win the league heading into the season.
"If you asked me back in October, I would say, man, I hope we finish middle of the pack in the SEC," she said. "I didn't know, nor did any of us."
Florida coach Tim Walton recalls talking to Gasso after Oklahoma clinched the conference regular-season title.
"I congratulated her at home plate," he said. "And she gave me a look, and she said, "Did we? Because it certainly didn't feel like it." I think that's a pretty good quote. It's her quote to me, but I think that sums up just how tough this league was this year."
Sisters Kedre and Kai Luschar have been dominant in helping Oregon reach the World Series.
Kedre, a senior who is the younger of the two, leads the team with a .444 batting average, 61 RBIs and 17 doubles. She has scored 59 runs and has 29 stolen bases.
Kai Luschar, a fifth-year senior, is second on the team with a .421 average. She leads the nation with 59 stolen bases and has scored 63 runs.
Ole Miss is the only unseeded team remaining. The Rebels beat Arizona twice to win the Tucson Regional and beat Arkansas in super regionals.
The Rebels aren't just here to show up.
"So proud of the journey and the season that we've had," Ole Miss coach Jamie Trachsel said. "We have one more chapter in our story, and we're looking forward to having a lot to say about it here in Oklahoma City."
UCLA and Oregon will meet in a matchup of former Pac-12 teams that moved to the Big Ten this year.
UCLA looks to add to its record 12 World Series titles with a pair of sluggers leading the way. Megan Grant has 25 home runs and 79 RBIs and Jordan Woolery has 23 homers and 86 RBIs, and they give the Bruins a legitimate chance to add to that total.
Oregon was the Big Ten regular-season champion. The Ducks beat UCLA in two out of three meetings during a series in April.
Bruins coach Kelly Inouye-Perez said her team has improved since then.
"What I learned most was our best is yet to come," she said. "We didn't play our best ball."
Texas Tech pitcher NiJaree Canady had a goal to get her new team to the World Series, and she delivered.
The star pitcher was the USA Softball Collegiate Player of the Year last season for Stanford. She helped the Cardinal reach the national semifinals two straight years before joining the Red Raiders.
This season, she helped Tech win the Big 12 regular season title, then the tournament. The Red Raiders finally accomplished the goal of reaching the World Series by upsetting No. 5 seed Florida State in super regional play.