Re: Best and Worst
Best: Probably her 2005 Wimbledon final victory over Davenport. Without that win, Venus would be almost 4 years since she played her best tennis. We would have far less basis for believing she could still possibly win more slams, and she would be long past her peak. That is because, of course, she has achieved very little else of note since cApril 2004.
Worst: Although it's not her worst loss in terms of quality of opponent, I would argue that her 2001 opening round French Open loss to Schett was a wasted opportunity. She had played well on clay and was looking like a strong contender for the title.
Best: I think her best win would have to be her 2001 victory over Davenport at the U.S Open, in the quarter-finals. It's a strange choice, but I think it was then that she proved that the Williams sisters were leaving Hingis, Davenport and Capriati behind. With the exception of her rather tame loss to Venus in the final of that year, I don't think Serena ever really looked back after that. She knew inside that if she remained fit and focused, 2002 would be her year.
Worst: Some of those losses to Venus were pretty dismal. But I think the one which springs to mind most of all is her Wimbledon 2005 loss to Craybas. I don't think she has ever lost to, with all due respect to Craybas, so light-weight an opponent in a grandslam.