Who will challenge top-seed Cal?

1. Can California be stopped?

A season ago, the No. 1 ranking in the ESPN.com/USA Softball Top 25 passed between eight teams before Arizona State finally took the top spot for good in late April and raced with relative ease to its second national championship in four seasons. It took far less time for a favorite to emerge this season, and that's no coincidence. California really is that good.

Coach Diane Ninemire's team claimed the top spot in the poll after just one week of play and held it for all but one week of the regular season. The Bears won their first outright conference title since 1987, something they didn't even manage en route to a national championship in 2002. They returned the entire lineup from the team that reached the Women's College World Series last season, including pitching ace Jolene Henderson. They added three impact freshmen starters in Danielle Henderson (Jolene's little sister), Cheyenne Cordes and Breana Kostreba and welcomed back fifth-year senior All-American Valerie Arioto from a redshirt 2011 season.

With the Pac-12 title on the line against Arizona State in the final weekend of the regular season, all Arioto did was hit a walk-off home run in the opening game and strike out 11 batters en route to pitching a shutout in the second game.

So should we even bother sweating out a week in the Oklahoma City heat for the Women's College World Series?

Of course we should, and not just because there are few atmospheres in women's sports quite like that inside Hall of Fame Stadium. Arizona State lived up to the label of favorite last season, but that was the first time since Arizona won it all in 2006 that the No. 1 team at the end of the regular season won the title. Cal is the clear favorite. It hits for power, has speed at the top of the lineup, plays fantastic defense and has two pitchers it can trust in any situation. But there are three teams that could wrestle away the title without stunning the softball world in the process.

Bama Alabama: No team in this quartet of top contenders has more experience in the starting lineup than Alabama, which regularly starts five seniors who are seeking their third trip to the World Series (or a fourth in the case of redshirt senior Amanda Locke). The Crimson Tide lead the nation in home runs but also have a one-two speed punch at the top of the lineup as good as any in Kayla Braud and Jen Fenton. Sophomore ace Jackie Traina is one of the stars of the tournament and only seems to get better as the pressure mounts, both in the circle and as a middle-of-the-order power hitter, although she's also probably going to have to throw every inning in the postseason. Alabama has a bit of a tortured history in the World Series, but this particular edition seems to take satisfaction in blazing its own trail.

ASU Arizona State: The Sun Devils are responsible for one of Cal's four losses, even if that came on the final day of the regular season after Cal took the first two games of the series to clinch the Pac-12 Conference title. The defending champions look quite a bit different than the team that won it all last season, but they still look capable of hoisting the trophy. The pitching star of last season's World Series as a freshman, Dallas Escobedo, had her share of ups and downs as a sophomore, but Escobedo is still one of the most physically gifted pitchers in the field, and with a deep, potent offense led by player of the year candidate Katelyn Boyd, neither Escobedo nor senior pitcher Hillary Bach need to be perfect.

OU Oklahoma: The Sooners share some similarities with the Bears. They made the World Series a season ago despite losing Jessica Shults, arguably their best hitter for the postseason due to an illness. But since returning, the junior catcher is back to her All-American form. Also like Cal, the Sooners are bolstered by impact freshmen in the form of Australian Georgia Casey and slugger Lauren Chamberlain, whose 25 home runs set a Big 12 single-season record. The biggest reason to think the Sooners could win on home soil is 6-foot-2 Keilani Ricketts, one of the most intimidating players in the sport as both a pitcher and a hitter.

2. What are five other names you need to know?

Lexy Bennett, Texas: All eyes are going to be on Texas anyway, as the No. 6 seed attempts to advance past regional play for the first time since Cat Osterman moved on in 2006. Bennett, with a .707 slugging percentage, .475 on-base percentage and double-digit home runs and stolen bases is the key figure in an offense that should end that drought.

Kayla Braud, Alabama: The Crimson Tide hit 90 home runs, but the lineup bellwether is the leadoff hitter who hit just one out of the park. Braud actually has power of her own when she swings away, but she's at her best slapping, bunting and causing havoc in the infield. She has been on a tear of late after a slow start this season, at least by her standards.

Mel Dumezich, Texas A&M: The Aggies' ace still doesn't get all the attention her play merits, but she's as valuable a two-way player as anyone this side of Ricketts and Arioto. The junior went 28-11 and took her offensive production to new heights in hitting .304 with 17 home runs.

Alix Johnson, Arizona State: Coach Clint Myers inherited the star on his first championship team in 2008, Kaitlin Cochran, but he's had little difficulty replenishing the ranks. Boyd was first, but Johnson is next. The sophomore hit .385 with five home runs and 25 RBIs in conference games and trailed only Boyd and Arioto in on-base percentage and slugging percentage among Pac-12 players in all games.

Chelsea Thomas, Missouri: The Tigers had one of the strongest closing kicks leading into NCAA tournament play, earning the No. 9 seed after it looked for a time like they might be well into double digits. A lot of the top seeds will breathe a sigh of relief about that because beating Thomas, who is 23-7 with a 1.07 ERA, two out of three times in a super regional would be one of the toughest tasks in the tournament.

3. Who are four pitchers on unseeded teams no one wants to face this weekend?

Jenna Caira, Syracuse: The cap-sporting Canadian can twist hitters into pretzels with one of the best changeups in college softball. She went 25-7 with a 1.56 ERA this season for the Orange and raised her strikeout rate while lowering her home-run rate. With two NCAA tournaments and international experience with Canada already under her belt, she won't be rattled by the prospect of potentially facing defending national champion Arizona State in the Tempe Regional. As Taryne Mowatt showed time and again not too long ago, even Pac-12 hitters can struggle against a good changeup.

Rachele Fico, LSU: The good news for No. 8 Texas A&M and others in the College Station Regional is that they likely won't have to score many runs to beat an LSU team that simply cannot hit. The bad news is no opponent is likely to score much against Fico. The much-hyped pitcher from Connecticut had her moments as a freshman and some success as a sophomore, but this season she has become the ace so many expected her to be. Ignore the 16-11 record and look at the 0.98 ERA and .181 batting average against. On any given day, she can win a 1-0 game against any team in the country.

Stephanie Ricketts, Hawaii: One year after Oklahoma's Keilani Ricketts played a part in beating Arizona in a super regional in Tucson, her older sister will try her hand at the even more unthinkable -- eliminating the Wildcats at home in a regional. Hawaii's ace ranked sixth in the nation in ERA entering last week, and lest anyone think that's all schedule-aided, it includes 10 innings in which she allowed no earned runs and struck out 12 in a win against Cal.

Jessica Simpson, Miami (Ohio): Sure, the name grabs your attention (former Colorado basketball player Brittney Spears can commiserate), but opponents in the Knoxville Regional, including No. 7 Tennessee, will have their work cut out for them against a senior who went 31-13 with a 1.06 ERA and 346 strikeouts in the regular season. When her team needed three wins in one day in the MAC tournament just to make the NCAA tournament, Simpson delivered 23 strikeouts in 21 innings without allowing an earned run.

4. What are the toughest regionals?

Gainesville (No. 5 Florida, South Florida, Central Florida, Florida Gulf Coast).

Florida coach Tim Walton makes no secret of the fact that his young team is struggling with confidence at the moment. The Gators made it to the SEC tournament championship game last weekend, but they scored just four runs in three games in that event, pulling out a 1-0 win against LSU and a 2-1 win against Tennessee before a 10-1 loss against Alabama. The last thing an offense lacking confidence needs to see in a regional is shutdown pitching, but at least two candidates for just that label are headed to Gainesville in what could be a tense weekend of low-scoring softball. South Florida's Sara Nevins is one of 11 finalists for USA Softball Player of the Year, the product of a 26-4 record and 1.04 ERA. One of those losses came at the hands of the Gators in February, but she allowed just five hits in 7.1 innings. Despite her years, Central Florida freshman Mackenzie Audas has even more reason for confidence. It was just a month ago that she blanked the Gators, striking out 11 batters and allowing just two hits. On the season, she's 21-10 with a 1.21 ERA and 261 strikeouts in 219.1 innings.

Louisville (No. 15 Louisville, Kentucky, Michigan, Valparaiso).

There's a danger sometimes in separating the most difficult draw from the one with the most recognizable names, but the games in Louisville qualify on both counts. This is not the same Michigan team that has been in or around the World Series so much in recent seasons, but it has some veteran bats and its freshman pitching duo of Haylie Wagner and Sara Driesenga held up over the long season. In addition to beating Kentucky and dropping a 2-1 decision at Louisville earlier this season, the Wolverines also beat UCLA and Auburn and lost by a run against Arizona State and two runs against Oklahoma.

Speaking of Kentucky, no team played any better down the stretch, undone only by a slow start in an SEC tournament quarterfinal against Georgia. Third baseman Brittany Cervantes might be the best player in this regional, and while senior pitcher Chanda Bell has her ups and downs, the ups are very, very good. And all of that is just about the second and third seeds in the draw. Host Louisville will be eager to prove its sweep of the Big East regular season and tournament titles deserved better than this seed.

5. Which teams could surprise?

Could reach a super regional: Texas State

File away the name Chandler Hall. With Dumezich, Fico and LSU's Brittany Mack around, the College Station Regional isn't short on quality pitching, but Texas State's Hall deserves to be included in that group. The Bobcats aren't an offensive juggernaut -- they've hit just nine home runs all season -- but their offense matches up on even footing with LSU in the opener for both teams. And given a fair fight, Hall (21-6, 1.63 ERA and 199 strikeouts in 175.2 innings) could keep them in the winner's bracket. The Bobcats also have another quality pitcher in Anne Marie Taylor, giving them a chance to hang around.

Could reach the World Series: Hawaii

Going through Arizona in a regional in Tucson and presumably Oklahoma in a super regional in Norman is about as tough as it gets, but Hawaii is at least used to hitting the road in the postseason. The Rainbow Wahine have two quality pitchers in Ricketts and Parnaby, so if one doesn't have her best stuff on a given day, coach Bob Coolen has options. And while this Hawaii team doesn't hit like the team that set an NCAA single-season record for home runs en route to the 2010 World Series, it does have game-changing offensive talents in Jessica Iwata and Kelly Majam.