Serena saved three set points there, but then set up a fourth when she ended a 14-stroke exchange by shanking a backhand volley several feet wide of the doubles alley. Serena put a palm up, then put her racket head-down on the court and leaned her forehand on the end of the handle, a vision of exasperation.

On the next point, Serena weakly put a backhand into the net, ending the set.

“I mean, to be honest, she did help me,” Srebotnik said.

The second set saw more of the same: Srebotnik mixing speeds, and Serena flubbing shots she usually puts away. Ahead 2-1, Serena earned two break points, wasting each with a forehand into the net. Ahead 3-2, she earned two more, but missed a backhand return then drove a forehand into the net.

Serena had her last break chance at 4-3, and she gave it away by badly missing a drop shot. She tugged the brim of her beige ballcap low over her eyes, perhaps trying to hide the disappointment.

Srebotnik won the next point with a volley winner, then watched Serena be her own worst enemy again. Srebotnik put up a defensive lob, completely out of position; a tap-in probably would have sufficed for Serena. Instead, she tried to hammer the ball and put it in the net.

“I just missed some easy shots. I think that was the difference,” Serena said. “And she made hers.”

Suddenly serving for the biggest victory of her singles career, Srebotnik let two match points slip away. On No. 3, though, Serena pulled a forehand well wide.

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“It’s like she wasn’t there mentally. ... I’m really trying to figure this one out,” Price said.

Serena stared blankly and spoke slowly during her postmatch news conference. She was asked if “puzzled” would describe how she felt.

“No, I’m not puzzled at all,” she said. “I just don’t want to be here.”

Now, Srebotnik will play No. 10 Patty Schnyder of Switzerland, and Pennetta will face qualifier Carla Suarez Navarro of Spain.

“I don’t want to be satisfied,” Pennetta said. “It’s Roland Garros. To even think about reaching the quarterfinals or semifinals at a tournament like this is what anyone who plays tennis dreams about.”

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