STANFORD -- Two weeks ago, the 2013 Bank of the West Classic was shaping up as a real classic, even without defending champion Serena Williams in the field.

The longest-running women's-only tennis tournament in the world had lined up second-ranked Maria Sharapova, plus all four Wimbledon semifinalists led by longtime Bank of the West favorite Marion Bartoli, who claimed her first Grand Slam title at the All England Club on July 6.

But then the bombs dropped. Still recovering from a hip injury suffered at Wimbledon, headliner Sharapova pulled out just a week before Monday's official start of the event at Stanford's Taube Family Tennis Stadium.

Sharapova's exit was followed by that of Germany's Sabine Lisicki, who made such a fabulous run to the Wimbledon final, due to a wrist injury. Then semifinalist Kirsten Flipkens pulled out for undisclosed reasons. Finally, Bartoli withdrew Thursday with a hamstring issue.

Needless to say, Bank of the West tournament director Kim Hall has had better weeks, even though last-minute injury withdrawals are a fact of life on both the men's and women's pro tennis circuits.

"There are always four or five pullouts on average in any tournament," said Hall. "But I don't know if we've ever had this many. Our field was looking really great, but we just got hit by the injury bug. So many players in the top 10 are banged right now."

Hall added that in an attempt to try and fill the void of four top-20 players lost, a concerted effort was staged to try and convince Williams to rework the Bank of the West event back into her summer schedule and defend her title.

"We were still talking to Serena up until Tuesday," Hall said. "And she was still entertaining the option of coming here until a few days ago."

Williams elected to stay in Europe following Wimbledon, and this past week played in the Swedish Open, which she won Sunday after decimating a decidedly undistinguished field. Even though she made the long trip to Palo Alto last year just a day after winning Wimbledon, she elected not to make such an exhausting intercontinental jaunt this year.

Hence, the Bank of the West will have just one of the world's top 10 players in its field this week -- fourth-ranked Agnieszka Radwanska of Poland. She's the top seed, as expected, and a worthy one. At 24, she already has 12 WTA titles and is really only missing a Grand Slam title to be regarded as an elite player. That said, she is the only player in the world to have reached the quarterfinals of all three Grand Slams played so far this year. She lost in the Wimbledon semis to Lisicki in three sets.

As for the rest of the field, Hall thinks it's just fine, all things considered. No. 2 seed Samantha Stosur of Australia, ranked 13th, won the 2011 U.S. Open by beating Williams, and the field also includes 2010 French Open champ Francesca Schiavone, although Schiavone has dropped to 59th in the world and is unseeded at the Bank of the West.

The top four seeds all drew first-round byes. Stosur will headline the Tuesday evening session while Radwanska makes her tournament debut Wednesday night.

The real hook for the tournament, though, could be the bevy of up-and-coming potential American stars in the field, led by 18-year-old Madison Keys of Boca Raton, Fla. The 5-foot-10 Keys already possesses a lethal serve that has been compared to Williams', and she gave Radwanska all she could handle at Wimbledon in a three-set, third-round loss.

Keys is making her Bay Area debut, and considering the diminished field, this tournament could serve as a breakthrough for her, even though she is unseeded. She plays No. 8 seed Magdalena Rabarikova of Slovakia in the opening round Monday at 7 p.m.

"Everybody in the industry is talking about Madison and I think most feel she's the next American star," said Hall. "She's the youngest player in the top 50 (No. 44). She has the tools to compete in the Grand Slams once she puts it all together, and I think she's going to get there. She's definitely one to watch."

Other top young Americans in the field include 23-year-old Jamie Hampton, who is fourth-seeded, along with former Stanford standouts Nicole Gibbs and Mallory Burdette.

In short, despite all the commitment setbacks, Hall is not worried about ticket sales.

"I think we're still tracking above last year's numbers, so we're feeling fine about that," she said.