She then dominated the rest of the way Saturday to beat Karin Knapp 7-6 (4), 6-0 in the third round of the French Open.
The top-ranked Sharapova needed 81 minutes to win the opening set. She squandered a lead and fell behind in the tiebreaker, then benefited from some shaky shots by Knapp. But beginning with that ferocious backhand, Sharapova played her best tennis of the week.
"It was like my twin sister was here, and then Maria actually made her flight and made it for the second set," Sharapova said. "I definitely became a lot more aggressive and stepped in and didn't give her too many easy balls."
Top-ranked Roger Federer was aggressive from the start and defeated Mario Ancic 6-3, 6-4, 6-2. Ancic is the last player to beat Federer at Wimbledon -- in 2002 -- but has lost their past five meetings.
Federer will next play unseeded Frenchman Julien Benneteau, who beat Robin Soderling 1-6, 7-6 (6), 6-0, 6-1, then threw his shirt and shoes to the jubilant crowd.
The lone remaining American in either draw, Robby Ginepri, won again and became the first U.S. man to reach the fourth round at Roland Garros since Andre Agassi in 2003.
Ginepri extended his improbable run by beating Frenchman Florent Serra 6-4, 6-4, 6-4.
"I would definitely like to have a lot of the other Americans still in the tournament," Ginepri said. "I'm really not trying to let that weigh on my shoulders."
Ginepri, ranked 88th, came into the tournament 6-24 on clay and 0-5 at the French Open, but he has now reached the final 16 at all four Grand Slam events.
He was steadier than Serra, losing serve just once and committing only 18 unforced errors to 43 for the Frenchman. Ginepri said he has benefited from the coaching of Jose Higueras and Diego Moyano.
"Talking with both of them has really opened up another door with me on the clay court," Ginepri said. "Before I really had no clue how to construct points or what type of shots to hit when I was in trouble or how to serve, what sets up what. So with them having a lot of experience and just with me listening constantly, it's just started being engraved into my mind."
No. 4 Nikolay Davydenko blew a big lead and lost to No. 28 Ivan Ljubicic 4-6, 2-6, 6-3, 6-2, 6-4. No. 5 David Ferrer won a seesaw marathon against No. 25 Lleyton Hewitt 6-2, 3-6, 3-6, 6-3, 6-4.