Two-time US Open champion Venus Williams suffered her most lopsided loss in 24 appearances at the Grand Slam tournament with a 6-1 6-1 defeat at the hands of qualifier Greet Minnen in the first round on Tuesday.

The German smacked 24 winners and saved all six break points she faced to dispatch the veteran American, who she reveres.

"In 1997, Venus already played a final here and I was just born, so for me it was incredible to play a legend like her," the 26-year-old Minnen said in an on-court interview.

"I have huge respect for her."

Former world No 1 Williams' best chance of climbing back into the contest came when she had a break point opportunity in the opening game of the second set but she failed to convert.

The hard-hitting Minnen would break the next game at love and cruise to victory in the match that lasted just 75 minutes.

"First I have to give credit to my opponent," Williams told reporters.

"There wasn't a shot she couldn't make. Even when I hit really amazing shots, she just hit a winner or a dropshot, so I don't think I played badly. I think it was just one of those days where it's just unlucky."

Seven-time Grand Slam winner Williams, whose younger sister Serena retired after last year's US Open with 23 major titles to her name, said she was prepared to come to Flushing Meadows without her sibling playing.

"I was very much aware that Serena wouldn't be playing the tournament, so I think I was okay. I've had a chance to get used to that idea even before she retired," she said.

"I kind of knew that was coming."

Asked when she might hang up her racket, Williams was non-committal.

"I wouldn't tell you," she said with a smile.

"I don't know. I don't know why you're asking."