Sharapova, ranked No. 2 in the world and the tournament's biggest name along with Wimbledon champion Marion Bartoli, has been forced to withdraw due to a left hip injury suffered during Wimbledon.
"We are disappointed for our fans that Maria won't be able to attend this year's Bank of the West Classic but unfortunately injuries are a part of the sport and we understand that a player's health must always come first," said Bank of the West Classic Tournament Director Kim Hall. "We wish her a speedy recovery and hope she is able to return to the court soon."
The tournament was also was notified Monday that Kirsten Flipkens of Belgium has also withdrawn. She was one of four Bank of the West entrants to reach Wimbledon's semifinals.
With those withdrawals, former world No. 4 Daniela Hantuchova and up-and-coming American Christina McHale have received berths into the main draw.
In addition, the Bank of the West Classic announced Monday that it has granted a wild card into the main draw to Burdette.
Burdette, who turned professional shortly after last year's Bank of the West Classic, reached the third round of last year's US Open and has risen quickly up the world rankings. She is currently No. 78 and will join former Cardinal teammate Nicole Gibbs next week.
The Bank of the West Classic still boasts a strong player field including reigning Wimbledon champion Bartoli, current world No. 4 Agnieszka Radwanska, 2011 US Open champion Samantha Stosur and 2010 French Open champion Francesca Schiavone.
The Bank of the West Classic is the longest-running women-only professional tennis tournament in the world and is the first stop of the Emirates Airline US Open Series. Owned and operated by IMG, the WTA Premier event features a 28-player singles draw and a 16-team doubles draw with total prize money of $795,000.
Television coverage begins on July 25 on the Tennis Channel from 2-6 p.m., and 7-9 p.m. ESPN2 will televise singles quarterfinals live on Friday, July 26 from 8-10 p.m. Saturday's singles semifinals (7-9 p.m.) will be shown live by ESPN2, as will the singles finale on Sunday from 2-4 p.m.
Tickets can be purchased by calling the box office at 866-WTA-TIXS (866-982-8497) or by logging on to www.BankoftheWestClassic.com.
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Nicole Gibbs has picked up right where she left off when she helped the Stanford women's tennis team win the NCAA championship in May.
Gibbs defeated Croatia's Ivana Lisjak, 6-1, 6-4, in the championship match of the Yakima Regional Hospital Challenger on Sunday in Washington state.
Gibbs, ranked No. 205 this week following her career best 172 last week, claimed her third career ITF singles title, but her first since turning pro after completing her junior season with the Cardinal on a successful note.
"First title as a pro player!!" she tweeted. "Excited to start all over in Portland on Weds."
Her NCAA singles championship victory over Nebraska's Mary Weatherholt, 6-2, 6-4, was her final amateur match, ending a Cardinal career that saw her win 30 of the 31 career matches she played in May. Her lone loss was to eventual 2011 champion Jana Juricova of California in the semifinal.
Gibbs' last title was in July of last year, when she beat Julie Coin in three sets in Denver. She played as an amateur. She also improved to 4-4 in ITF final matches.
Gibbs, seeded eighth, went three sets to beat Israel's No. 1 ranked woman Julia Glushko, 6-4, 2-6, 6-1, in the semifinals.
Lisjak came into the tournament with seven ITF titles, but the 26-year-old was looking for her first since October of 2010, when Gibbs was just beginning her freshman year at Stanford.
Gibbs, 91-60 as a singles player on the tour, began play Wednesday in the $50,000 Oregon Challenger at the Tualatin Hills Tennis Center in Beaverton. She opened with a 6-3, 6-3 victory over Nicole Melichar, earning a date with No. 2 seed Masaki Doi of Japan in the next round Thursday.
Stanford sophomore Krista Hardebeck lost her opener in Oregon in straight sets.
Gibbs received a wild card into the Bank of the West Classic and will play in her third straight tournament in as many weeks beginning next week. She won her opener last season before having to play eventual champion Serena Williams in Round 2. Williams won, 6-2, 6-1, and won three more times to earn the $96,000 winner's check.
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The qualifying tournament begins Saturday and continues through Monday morning.
One of the bigger names competing in qualifying this year is Kimiko Date-Krumm. She has five career titles to her credit and reached the third round of both Wimbledon and the Australian Open this year. Date-Krumm was once ranked as high as No. 4 in the world.
Last year's runner-up Coco Vandeweghe will be making her third straight appearance. Last year, she received a lucky loser entry into the main draw and made the most of the opportunity recording wins over No. 4 seed Jelena Jankovic and No. 5 seed Yanina Wickmayer en route to the final.
Michelle Larcher De Brito will also be competing in qualifying rounds. She upset Sharapova in the second round of this year's Wimbledon Championships.
Marina Erakovic who made the third round at Wimbledon and the French Open this year is also slotted to compete in this year's qualifying draw. Erakovic won the US National Indoor Championships at Memphis earlier this year.
And, Melanie Oudin is also scheduled to compete in qualifying. Oudin made a name for herself when she advanced to the quarterfinals of the 2009 US Open. Oudin will be making her third appearance at the Bank of the West Classic and her first since 2010.