"It wasn't me out there today," said Sharapova, who struggled throughout the match with an inflamed chest muscle that limited her power. "I'm serving 93 miles per hour and not hitting my forehand. With that, it's tough to come out against a player that has nothing to lose."
Chakvetadze suffered a groin injury during the contest, breaking into tears after the match.
Tonight in L.A. the Russian former Wimbledon champ is scheduled to play for the No. 1 ranking, with a quarterfinal win over No. 9 seed Daniela Hantuchova propelling her to the top spot on the WTA Tour Rankings, supplanting current No. 1 Lindsay Davenport.
But Sharapova says she is doubtful for the match Friday night, suffering a cold on top of the muscle injury.
"It's been an on and off problem for me," said Sharapova on the pec injury. "I don't think the pain is going to go away with me trying to play and hit as hard as I can. There's no (No. 1 ranking) pressure at all -- it's not important for me to play (Friday night)."
Although tournament officials, who are putting on their Sharapova bobblehead promotion Friday night and have the Russian in the prime ESPN viewing slot, might disagree.
Other seeds into the quarters Thursday were (3) Elena Dementieva (d. (17) Bartoli), (4) Nadia Petrova (d. (15) Koukalova), (5) Kim Clijsters (d. (12) Safina, bagel in the first set), (9) Hantuchova (d. (Q) K.Bondarenko), and (13) Francesca Schiavone (d. (LL) Lepchenko in three).
"My mind was going and I was thinking maybe it was too easy for me," said Clijsters after bageling Safina in the first set. "But I ended well and that's the most important thing."
Two unseeded players also busted the seeded quarterfinal party in Italian qualifier Tathiana Garbin (d. Raymond), and the former No. 2-ranked Conchita Martinez (d. Daniilidou who retired in the second set with an ankle sprain).
Friday's quarterfinal line-up is (5) Clijsters vs. (4) Petrova, (13) Schiavone vs. Martinez, (3) Dementieva vs. (Q) Garbin, and in the night match (1) Sharapova vs. (9) Hantuchova.
