Serena advances to quarterfinals.(Chicago Tribune)

NEW YORK_As a German man awaited a court appearance for the latest in a series of stalking incidents involving top-ranked Serena Williams, the tennis player's father expressed concern that his daughter doesn't fully realize how much jeopardy she might be in.

"This guy could have got in and hurt Serena," Richard Williams said. "I don't think Serena takes it seriously enough. She's 20 years old. As a father it really concerns me."

Serena Williams dispensed with 20th-seeded Daja Bedanova 6-1, 6-1 in 41 minutes Sunday to advance to the U.S. Open quarterfinals. As she waited out a day-long rain delay in the players' lounge, Williams, who has said in the past that she has tried to shut out the incidents to retain her competitive focus, admitted her father might have a point.

"Probably not," Williams said when asked if she had given the incidents their proper weight.

She has taken the precaution, however, of traveling with bodyguard Dario Valli since this spring.

"It's a little bit nerve-wracking and scary," Williams said with Valli at her side. "I'm definitely watching my back and being careful. But I can't let it stop my life."

Albrecht Stromeyer, 34, of Frankfurt, is charged with two counts of stalking and jailed on $3,000 bond pending a Thursday court hearing in Queens. He faces a $1,000 fine and up to a year in prison if convicted of the stalking charges.